// bsls_compilerfeatures.h                                            -*-C++-*-
#ifndef INCLUDED_BSLS_COMPILERFEATURES
#define INCLUDED_BSLS_COMPILERFEATURES

#include <bsls_ident.h>
BSLS_IDENT("$Id: $")

//@PURPOSE: Provide macros to identify compiler support for C++11 features.
//
//@MACROS:
//  BSLS_COMPILERFEATURES_CPLUSPLUS: portable version of `__cplusplus`
//  BSLS_COMPILERFEATURES_FORWARD_REF(T): argument of type `T` to be forwarded
//  BSLS_COMPILERFEATURES_FORWARD(T, V): forward argument `V` of type `T`
//  BSLS_COMPILERFEATURES_FULL_CPP11: indiates all c++11 features available
//  BSLS_COMPILERFEATURES_FULL_CPP14: indiates all c++14 features available
//  BSLS_COMPILERFEATURES_FULL_CPP17: indiates all c++17 features available
//  BSLS_COMPILERFEATURES_FULL_CPP20: indiates all c++20 features available
//  BSLS_COMPILERFEATURES_GUARANTEED_COPY_ELISION: flag for return optimization
//  BSLS_COMPILERFEATURES_INITIALIZER_LIST_LEAKS_ON_EXCEPTIONS: compiler bug
//  BSLS_COMPILERFEATURES_PP_LINE_IS_ON_FIRST: `__LINE__` value for multi-line
//  BSLS_COMPILERFEATURES_SUPPORT_ALIAS_TEMPLATES: flag for alias templates
//  BSLS_COMPILERFEATURES_SUPPORT_ALIGNAS: flag for `alignas`
//  BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_FALLTHROUGH: `[[fallthrough]]`
//  BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_MAYBE_UNUSED: `[[maybe_unused]]`
//  BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_NODISCARD: `[[nodiscard]]`
//  BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_NORETURN: `[[noreturn]]` attribute
//  BSLS_COMPILERFEATURES_SUPPORT_CONCEPTS: C++20 core language concepts
//  BSLS_COMPILERFEATURES_SUPPORT_CONSTEVAL_CPP20: `consteval` specifier
//  BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR: `constexpr` specifier
//  BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR_CPP14: C++14 `constexpr` spec.
//  BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR_CPP17: C++17 `constexpr` spec.
//  BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR_CPP20: C++20 'constexpr' spec.
//  BSLS_COMPILERFEATURES_SUPPORT_COROUTINE: core & lib C++20 coroutine support
//  BSLS_COMPILERFEATURES_SUPPORT_CTAD: flag for template argument deduction
//  BSLS_COMPILERFEATURES_SUPPORT_DECLTYPE: flag for `decltype`
//  BSLS_COMPILERFEATURES_SUPPORT_DEFAULT_TEMPLATE_ARGS: for function templates
//  BSLS_COMPILERFEATURES_SUPPORT_DEFAULTED_FUNCTIONS: explicit `= default`
//  BSLS_COMPILERFEATURES_SUPPORT_DELETED_FUNCTIONS: explicit `= deleted`
//  BSLS_COMPILERFEATURES_SUPPORT_ENUM_CLASS: flag for `enum class`
//  BSLS_COMPILERFEATURES_SUPPORT_EXTERN_TEMPLATE: flag for `extern template`
//  BSLS_COMPILERFEATURES_SUPPORT_FINAL: flag for `final` keyword
//  BSLS_COMPILERFEATURES_SUPPORT_GENERALIZED_INITIALIZERS: init.-list syntax
//  BSLS_COMPILERFEATURES_SUPPORT_HAS_INCLUDE: flag for `__has_include`
//  BSLS_COMPILERFEATURES_SUPPORT_HEXFLOAT_LITERALS: `0x1.5p+5` supported
//  BSLS_COMPILERFEATURES_SUPPORT_INCLUDE_NEXT: flag for `include_next`
//  BSLS_COMPILERFEATURES_SUPPORT_INLINE_NAMESPACE: flag for `inline namespace`
//  BSLS_COMPILERFEATURES_SUPPORT_INLINE_VARIABLES: flag for `inline` variables
//  BSLS_COMPILERFEATURES_SUPPORT_NOEXCEPT: `noexcept` operator
//  BSLS_COMPILERFEATURES_SUPPORT_NOEXCEPT_IN_FNC_TYPE: `noexcept` fnctype diff
//  BSLS_COMPILERFEATURES_SUPPORT_NOEXCEPT_TYPES: deprecated, see above
//  BSLS_COMPILERFEATURES_SUPPORT_NULLPTR: flag for `nullptr`
//  BSLS_COMPILERFEATURES_SUPPORT_OPERATOR_EXPLICIT: `explicit` operator
//  BSLS_COMPILERFEATURES_SUPPORT_OVERRIDE: `override` keyword
//  BSLS_COMPILERFEATURES_SUPPORT_RAW_STRINGS: C++11-style R"tag(string)tag"
//  BSLS_COMPILERFEATURES_SUPPORT_REF_QUALIFIERS: ref-qualified member function
//  BSLS_COMPILERFEATURES_SUPPORT_RVALUE_REFERENCES: flag for rvalue references
//  BSLS_COMPILERFEATURES_SUPPORT_STATIC_ASSERT: flag for `static_assert`
//  BSLS_COMPILERFEATURES_SUPPORT_STATIC_CALL_OPERATOR: `static operator()`
//  BSLS_COMPILERFEATURES_SUPPORT_THREE_WAY_COMPARISON: `<=>` operator
//  BSLS_COMPILERFEATURES_SUPPORT_THROW_SPECIFICATIONS: C++98 exception specs.
//  BSLS_COMPILERFEATURES_SUPPORT_TRAITS_HEADER: has `<type_traits>` header
//  BSLS_COMPILERFEATURES_SUPPORT_UNICODE_CHAR_TYPES: flag for `char(16|32)_t`
//  BSLS_COMPILERFEATURES_SUPPORT_USER_DEFINED_LITERALS: user-defined literals
//  BSLS_COMPILERFEATURES_SUPPORT_UTF8_CHAR_TYPE: flag for `char8_t`
//  BSLS_COMPILERFEATURES_SUPPORT_VARIABLE_TEMPLATES: variable templates flag
//  BSLS_COMPILERFEATURES_SUPPORT_VARIADIC_TEMPLATES: flag for variadic params.
//
//@SEE_ALSO: bsls_libraryfeatures, bsls_platform
//
//@DESCRIPTION: This component provides a suite of preprocessor macros to
// identify compiler-specific support of language features that may not be
// available on all compilers in use across an organization.  For example, as
// post-classic (C++11 and beyond) language facilities become more broadly
// available with sufficient quality (such as `extern template`) macros will be
// defined here to indicate whether the current platform/compiler combination
// supports the corresponding language features.  Note that in some cases,
// support for a given feature may need to  be explicitly enabled by using an
// appropriate compiler command-line option.
//
///Special Formatting Rules and Allowances
///---------------------------------------
// This header is a large and complex mesh of fairly unrelated and deep
// preprocessor conditionals with defining and undefining of many features
// macros.  It is hard for a human to scan this file and understand how and
// where particular feature macros are set.  To make matter more difficult in
// certain circumstances we also unset/undefine macros.  For this reason this
// header file uses a few special formatting rules to allow faster scanning:
//
// 1. Only comments and the `1` (replacement text) of {Binary Macros} may be 79
//    characters long (plus newline).  Line continuation characters in long
//    preprocessor conditionals etc. must be placed onto column 78.  This is to
//    allow a human to easily scan the file for places where feature macros are
//    being defined.
// 2. Feature macro definitions that are commented out (to indicate that for a
//    given compiler + standard library combination the support does not exist)
//    must not have the replacement text (the number 1) be present so as not to
//    confuse a human reader not using syntax highlighting.
// 3. Due to the depth of necessary conditional branches (`#if*`) and the
//    unusually long feature macro names defined in this header we use 2 spaces
//    indentation to ensure that most preprocessor directives don't wrap (and
//    become hard to read).
//
///Binary Macros
///-------------
// Binary macros defined in this file (such as the
// `BSLS_COMPILERFEATURES_SUPPORT_*` macros, and the
// `BSLS_COMPILERFEATURES_INITIALIZER_LIST_LEAKS_ON_EXCEPTIONS`, and the
// `BSLS_COMPILERFEATURES_PP_LINE_IS_ON_FIRST` macros) that represents a
// true/false preprocessor value are either undefined or defined to be the
// integer value 1.  This allows the traditional, idiomatic use of these macros
// where more brief preprocessor conditions rely on the fact that the C and C++
// preprocessors replace these unknown tokens with the value 0 in conditions:
// The following short condition
// ```
// #if BSLS_COMPILERFEATURES_SUPPORT_CTAD &&                                 /
//     BSLS_COMPILERFEATURES_SUPPORT_RVALUE_REFERENCES
//     #define U_TAKE_MY_FINAL_FORM                                          1
// #endif
// ```
// works identical to the following, longer one.
// ```
// #if defined(BSLS_COMPILERFEATURES_SUPPORT_CTAD) &&                        /
//     defined(BSLS_COMPILERFEATURES_SUPPORT_RVALUE_REFERENCES)
//     #define U_TAKE_MY_FINAL_FORM                                          1
// #endif
// ```
// Note that the line continuation backslash has been replaced with `/` to
// silence "multiline comment" warnings.
//
///Meaning of Platform Specific Macros
///-----------------------------------
// In this section we discuss the meaning of predefined platforms-specific
// macros where documentation is lacking or hard to find.
//
///Darwin
/// - - -
// Darwin has two compiler-relevant macros but much code often uses only one:
// `__APPLE_CC__` for both purposes.  This clarification is placed here so that
// we don't make the same mistake.
//
// * `__APPLE_CC__`: when defined it indicates that the *platform* to which we
//   compile is Darwin.  It does *not* mean that the compiler is made by Apple,
//   it is defined in 3rd party GCC or LLVM builds as well.  It identifies the
//   target operating system.  (Note that the value of this macro does not seem
//   to ever be larger than 6000.)
//
// * `__apple_build_version__`: when defined it indicates that the
//   (clang/clang++) compiler compiling the code is the one built by Apple.  It
//   will not be defined on 3rd party LLVM builds (such as those by brew.sh, or
//   MacPorts, or built-from-source).
//
///Macro Summary
///-------------
// The following are the macros provided by this component.  Note that they are
// not defined for all platform/compiler combinations.
//
// * `BSLS_COMPILERFEATURES_CPLUSPLUS`
//   > This macro provides a portable way to determine the version of the C++
//   > standard mode that is being used.  In general, this has the same value
//   > as the standard `__cplusplus` macro, but on some compilers with some
//   > settings the standard macro does not get assigned the correct value.
//   > The values generally set (as defined in the C++ Standard) are the year
//   > and month when the Standard was completed, and the value of this macro
//   > should be compared with the appropriate constants:
//   >  - 199711L -- before C++11
//   >  - 201103L -- C++11
//   >  - 201402L -- C++14
//   >  - 201703L -- C++17
//   >  - 202002L -- C++20
//   >  - 202302L -- C++23
//   > Note that compilers may report "in-between" values to indicate partial
//   > support of a standard, so `BSLS_COMPILERFEATURES_CPLUSPLUS > 201402L`
//   > normally means that *some* C++17 features are available.  Since those
//   > values are not standardized their meaning varies.
//
// * `BSLS_COMPILERFEATURES_FORWARD_REF(T)`
//   > This macro provides a portable way to declare a function template
//   > argument of type `T` that is to be perfect-forwarded.  The expansion of
//   > the macro will use syntax that is appropriate for the current compiler
//   > settings for this platform.
//
// * `BSLS_COMPILERFEATURES_FORWARD(T, V)`
//   > This macro provides a portable way to perfect-forward a function
//   > template argument, `V`, of type `T`.  The expansion of the macro will
//   > use syntax that is appropriate for the current compiler settings for
//   > this platform.  Note that due to the vagaries of implementing this
//   > macro, client code using this macro should provide the following two
//   > inclusions (in addition to the requisite inclusion of this header):
//   >  - `#include <bslmf_util.h>`
//   >  - `#include <bsls_util.h>`
//
// * `BSLS_COMPILERFEATURES_GUARANTEED_COPY_ELISION`
//   > This macro is defined if the compiler always elides all copies (or
//   > moves) when returning a prvalue expression from a function and using
//   > that expression to initialize a class object of the same type
//   > (ignoring cv qualifications).  Specifically, given the function,
//   > `Thing funcReturningThing() { return Thing(ctor-args...); }`, the
//   > return value is always initialized with `(ctor-args...)`; no copy is
//   > performed in the return statement.  Additionally,
//   > `Thing var(funcReturningThing())` always constructs `var` directly
//   > from the return expression of `funcReturningThing()`; again, no copies
//   > are involved.  The semantics of these optimizations are guaranteed in
//   > C++17 and later, but are optional in previous versions of C++.
//
//  * `BSLS_COMPILERFEATURES_FULL_CPP11`
//    > This macro is defined if the compiler supports all C++11 feature
//    > macros, and any other C++11 feature not described by the feature macros
//    > in this component.  If this macro is defined, code can assume that all
//    > C++11 feature macros are defined if this macro is defined.  Note that
//    > any component that relies on this macro will be incompatible with older
//    > compiler versions that do not define it.
//    > The list of C++11 feature macros is:
//    >..
//    >  BSLS_COMPILERFEATURES_SUPPORT_ALIAS_TEMPLATES
//    >  BSLS_COMPILERFEATURES_SUPPORT_ALIGNAS
//    >  BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_NORETURN
//    >  BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR
//    >  BSLS_COMPILERFEATURES_SUPPORT_DECLTYPE
//    >  BSLS_COMPILERFEATURES_SUPPORT_DEFAULT_TEMPLATE_ARGS
//    >  BSLS_COMPILERFEATURES_SUPPORT_DEFAULTED_FUNCTIONS
//    >  BSLS_COMPILERFEATURES_SUPPORT_DELETED_FUNCTIONS
//    >  BSLS_COMPILERFEATURES_SUPPORT_ENUM_CLASS
//    >  BSLS_COMPILERFEATURES_SUPPORT_EXTERN_TEMPLATE
//    >  BSLS_COMPILERFEATURES_SUPPORT_FINAL
//    >  BSLS_COMPILERFEATURES_SUPPORT_GENERALIZED_INITIALIZERS
//    >  BSLS_COMPILERFEATURES_SUPPORT_INLINE_NAMESPACE
//    >  BSLS_COMPILERFEATURES_SUPPORT_NOEXCEPT
//    >  BSLS_COMPILERFEATURES_SUPPORT_NULLPTR
//    >  BSLS_COMPILERFEATURES_SUPPORT_OPERATOR_EXPLICIT
//    >  BSLS_COMPILERFEATURES_SUPPORT_OVERRIDE
//    >  BSLS_COMPILERFEATURES_SUPPORT_RAW_STRINGS
//    >  BSLS_COMPILERFEATURES_SUPPORT_REF_QUALIFIERS
//    >  BSLS_COMPILERFEATURES_SUPPORT_RVALUE_REFERENCES
//    >  BSLS_COMPILERFEATURES_SUPPORT_STATIC_ASSERT
//    >  BSLS_COMPILERFEATURES_SUPPORT_TRAITS_HEADER
//    >  BSLS_COMPILERFEATURES_SUPPORT_UNICODE_CHAR_TYPES
//    >  BSLS_COMPILERFEATURES_SUPPORT_USER_DEFINED_LITERALS
//    >  BSLS_COMPILERFEATURES_SUPPORT_VARIADIC_TEMPLATES
//    >..
//
//  * `BSLS_COMPILERFEATURES_FULL_CPP14`
//    > This macro is defined if the compiler supports all C++14 feature
//    > macros, and any other C++14 feature not described by the feature macros
//    > in this component.  If this macro is defined, code can assume that all
//    > C++14 feature macros are defined if this macro is defined.  Note that
//    > any component that relies on this macro will be incompatible with older
//    > compiler versions that do not define it.
//    > The list of C++14 feature macros is:
//    >..
//    >  BSLS_COMPILERFEATURES_FULL_CPP11
//    >  BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR_CPP14
//    >  BSLS_COMPILERFEATURES_SUPPORT_VARIABLE_TEMPLATES
//    >..
//
//  * `BSLS_COMPILERFEATURES_FULL_CPP17`
//    > This macro is defined if the compiler supports all C++17 feature
//    > macros, and any other C++17 feature not described by the feature macros
//    > in this component.  If this macro is defined, code can assume that all
//    > C++17 feature macros are defined if this macro is defined.  Note that
//    > any component that relies on this macro will be incompatible with older
//    > compiler versions that do not define it.
//    > The list of C++17 feature macros is:
//    >..
//    >  BSLS_COMPILERFEATURES_FULL_CPP14
//    >  BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_FALLTHROUGH
//    >  BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_MAYBE_UNUSED
//    >  BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_NODISCARD
//    >  BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR_CPP17
//    >  BSLS_COMPILERFEATURES_SUPPORT_HAS_INCLUDE
//    >  BSLS_COMPILERFEATURES_SUPPORT_HEXFLOAT_LITERALS
//    >  BSLS_COMPILERFEATURES_SUPPORT_INLINE_VARIABLES
//    >  BSLS_COMPILERFEATURES_SUPPORT_NOEXCEPT_IN_FNC_TYPE
//    >  BSLS_COMPILERFEATURES_SUPPORT_NOEXCEPT_TYPES
//    >..
//
//  * `BSLS_COMPILERFEATURES_FULL_CPP20`
//    > This macro is defined if, with the exception of modules,  the compiler
//    > supports all C++20 feature macros, and any other C++20 feature not
//    > described by the feature macros in this component.  If this macro is
//    > defined, code can assume that all C++20 feature macros are defined.
//    > Support for modules can be determined independently of this macro by
//    > testing the standard feature test macro instead, `__cpp_modules`.
//    > Note that components relying on the `BSLS_COMPILERFEATURES_FULL_CPP20`
//    > macro will be incompatible with older compiler versions that do not
//    > define it.
//    > The list of C++20 feature macros is:
//    >..
//    >  BSLS_COMPILERFEATURES_FULL_CPP17
//    >  BSLS_COMPILERFEATURES_SUPPORT_CONCEPTS
//    >  BSLS_COMPILERFEATURES_SUPPORT_CONSTEVAL_CPP20
//    >  BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR_CPP20
//    >  BSLS_COMPILERFEATURES_SUPPORT_COROUTINE
//    >  BSLS_COMPILERFEATURES_SUPPORT_THREE_WAY_COMPARISON
//    >  BSLS_COMPILERFEATURES_SUPPORT_UTF8_CHAR_TYPE
//    >..
//
// * `BSLS_COMPILERFEATURES_INITIALIZER_LIST_LEAKS_ON_EXCEPTIONS`
//   > The `BSLS_COMPILERFEATURES_INITIALIZER_LIST_LEAKS_ON_EXCEPTIONS` macro
//   > is defined for implementations that leak temporary objects constructed
//   > trying to initialize a `std::initializer_list` object in the event that
//   > one of the elements of the list throws from its constructor.  This is
//   > known to affect gcc as recently as the 8.x series, and the Sun CC
//   > compiler in C++11 mode. This would often reveal itself as a spurious
//   > memory leak in exception-safety tests for `initializer_list`
//   > constructors, so rises to the level of a generally supported
//   > defect-detection macro.
//
// * `BSLS_COMPILERFEATURES_PP_LINE_IS_ON_FIRST`
//   > The `BSLS_COMPILERFEATURES_PP_LINE_IS_ON_FIRST` macro is defined for
//   > implementations that implement WG14 N2322
//   > (http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2322.htm)
//   > "Recommended practice" on the substitution value for the `__LINE__`
//   > (predefined) preprocessor macro when expanding a macro that uses
//   > `__LINE__` in its body, and that macro invocation spans multiple source
//   > lines (logical or physical).  When macro is defined `__LINE__` is
//   > substituted with the line number of the first character of the macro
//   > name of the (multi-line) macro invocation.  When this macro is not
//   > defined `__LINE__` is replaced (as traditional on older C++ compilers)
//   > by the line number of the last character of the  macro invocation that
//   > expands to a use of `__LINE__`.  See also {Example 2: `__LINE__` Macro
//   > Multi-line Value Differences Demonstration}.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_ALIAS_TEMPLATES`
//   > This macro is defined if alias templates are supported by the current
//   > compiler settings for this platform.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_ALIGNAS`
//   > This macro is defined if `alignas` alignment specifier is supported by
//   > the current compiler settings for this platform.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_FALLTHROUGH`
//   > This macro is defined if the `[[fallthrough]]` attribute is supported
//   > by the current compiler settings for this platform.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_MAYBE_UNUSED`
//   > This macro is defined if the `[[maybe_unused]]` attribute is supported
//   > by the current compiler settings for this platform.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_NODISCARD`
//   > This macro is defined if the `[[nodiscard]]` attribute is supported by
//   > the current compiler settings for this platform.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_NORETURN`
//   > This macro is defined if the `[[noreturn]]` attribute is supported by
//   > the current compiler settings for this platform.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_CONCEPTS`
//   > This macro is defined if the concepts core language feature is
//   > supported by the current compiler settings for this platform, as
//   > defined by ISO C++20.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_CONSTEVAL_CPP20`
//   > This macro is defined if `consteval`, as defined by ISO C++20, is
//   > supported by the current compiler settings for this platform.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR`
//   > This macro is defined if `constexpr` is supported by the current
//   > compiler settings for this platform.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR_CPP14`
//   > This macro is defined if `constexpr` with C++14 semantics is supported
//   > by the current compiler settings for this platform.  In particular,
//   > this allows multiple statements in a `constexpr` function; changing
//   > state of local variables within the function; and making non-`const`
//   > member functions `constexpr`.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR_CPP17`
//   > This macro is defined if `constexpr` with C++17 semantics is supported
//   > by the current compiler settings for this platform.  In particular,
//   > this allows lambda functions to be defined in a `constexpr` function.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR_CPP20`
//   > This macro is defined if 'constexpr' with C++20 semantics is supported
//   > by the current compiler settings for this platform.  In particular,
//   > this allows transient allocations.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_COROUTINE`
//   > This macro is defined if coroutines with C++20 (or later) semantics are
//   > supported by the current compiler settings, including the existence of
//   > the <coroutine> standard header that provides the basic library
//   > facilities necessary to make use of coroutines.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_CTAD`
//   > This macro is defined if template argument deduction introduced in the
//   > C++17 Standard are supported by the current compiler settings for this
//   > platform.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_DECLTYPE`
//   > This macro is defined if `decltype` is supported by the current
//   > compiler settings for this platform.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_DEFAULT_TEMPLATE_ARGS`
//   > This macro is defined if default template arguments for function
//   > templates are supported by the current compiler settings for this
//   > platform.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_DEFAULTED_FUNCTIONS`
//   > This macro is defined if defaulted functions are supported by the
//   > current compiler settings for this platform (i.e., via the `= default`
//   > syntax).
//
// * `BSLS_COMPILERFEATURES_SUPPORT_DELETED_FUNCTIONS`
//   > This macro is defined if deleted functions are supported by the
//   > current compiler settings for this platform (i.e., via the `= delete`
//   > syntax).
//
// * `BSLS_COMPILERFEATURES_SUPPORT_ENUM_CLASS`
//   > This macro is defined if `enum class` is supported by the current
//   > compiler settings for this platform.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_EXTERN_TEMPLATE`
//   > This macro is defined if `extern template` is supported by the current
//   > compiler settings for this platform.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_FINAL`
//   > This macro is defined if `final` is supported for classes and member
//   > functions by the current compiler settings for this platform.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_GENERALIZED_INITIALIZERS`
//   > This macro is defined if generalized initializers are supported by the
//   > current compiler settings for this platform.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_HAS_INCLUDE`
//   > This macro is defined if `__has_include` is supported by the current
//   > compiler settings for this platform.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_HEXFLOAT_LITERALS`
//   > This macro is defined if hexadecimal format literals for floating point
//   > types are supported by the current compiler settings for this platform.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_INCLUDE_NEXT`
//   > This macro is defined if `include_next` is supported by the current
//   > compiler settings for this platform.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_INLINE_NAMESPACE`
//   > This macro is defined if `inline` namespaces introduced in the C++11
//   > Standard are supported by the current compiler settings for this
//   > platform.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_INLINE_VARIABLES`
//   > This macro is defined if `inline` variables introduced in the C++17
//   > Standard are supported by the current compiler settings for this
//   > platform.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_NOEXCEPT`
//   > This macro is defined if the `noexcept` keyword is supported by the
//   > current compiler settings for this platform, both for designating a
//   > function as not throwing and for testing if an expression may throw.
//   > The definition of this macro does not depend on whether the current
//   > compiler configuration has disabled support for exceptions.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_NOEXCEPT_IN_FNC_TYPE`
//   > This macro is defined if the `noexcept` keyword is supported by the
//   > current compiler settings for this platform such that if `noexcept` is
//   > used to designate a function as not throwing, that use of `noexcept` is
//   > explicitly considered part of the type of the function (a feature
//   > introduced in C++17).  The definition of this macro does not depend on
//   > whether the current compiler configuration has disabled support for
//   > exceptions.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_NOEXCEPT_TYPES`
//   > Deprecated, use `BSLS_COMPILERFEATURES_SUPPORT_NOEXCEPT_IN_FNC_TYPE`
//   > instead.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_NULLPTR`
//   > This macro is defined if `nullptr` is supported by the current compiler
//   > settings for this platform.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_OPERATOR_EXPLICIT`
//   > This macro is defined if the `explicit` keyword applied to conversion
//   > operators is supported by the current compiler settings for this
//   > platform.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_OVERRIDE`
//   > This macro is defined if the `override` keyword is supported by the
//   > current compiler settings for this platform.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_RAW_STRINGS`
//   > This macro is defined if the compiler supports C++-11-style
//   > R"tag(string)tag" strings.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_REF_QUALIFIERS`
//   > This macro is defined if member functions with trailing reference
//   > qualifiers (e.g., `void myfunc(int) &&`) are supported by the current
//   > compiler settings for this platform.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_RVALUE_REFERENCES`
//   > This macro is defined if rvalue references are supported by the current
//   > compiler settings for this platform.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_STATIC_ASSERT`
//   > This macro is defined if `static_assert` is supported by the current
//   > compiler settings for this platform.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_STATIC_CALL_OPERATOR`
//   > This macro is defined if `static operator()` is supported by the current
//   > compiler settings for this platform.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_THREE_WAY_COMPARISON`
//   > This macro is defined if `<=>` operator is supported by the current
//   > compiler settings for this platform.  Including full library support as
//   > of C++20.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_THROW_SPECIFICATIONS`
//   > This macro is defined if dynamic exception specifications are supported
//   > by the current compiler settings for this platform.  Dynamic exception
//   > specifications were deprecated in C++11, and actively removed from the
//   > language in C++17.  The definition of this macro does not depend on
//   > whether the current compiler configuration has disabled support for
//   > exceptions.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_TRAITS_HEADER`
//   > This macro is defined if the standard library for the current compiler
//   > settings for this platform supports some form of the standard
//   > `<type_traits>` header.  Note that many standard library
//   > implementations provided partial support for a long time, and those
//   > libraries *will* be identified as providing the `<type_traits>` header.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_UNICODE_CHAR_TYPES`
//   > This macro is defined if the compiler supports the `char16_t` and
//   > `char32_t` types and the related u and U prefixes for character- and
//   > string-literal values.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_USER_DEFINED_LITERALS`
//   > This macro is defined if user-defined literals are supported by the
//   > current compiler settings for this platform.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_UTF8_CHAR_TYPE`
//   > This macro is defined if the compiler supports the `char8_t` type.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_VARIADIC_TEMPLATES`
//   > This macro is defined if variadic template parameters are supported by
//   > the current compiler settings for this platform.
//
// * `BSLS_COMPILERFEATURES_SUPPORT_VARIABLE_TEMPLATES`
//   > This macro is defined if variable templates introduced in the C++14
//   > Standard are supported by the current compiler settings for this
//   > platform.
//
///Usage
///-----
// The following code snippets illustrate use of this component.
//
///Example 1: Using `BSLS_COMPILERFEATURES_SUPPORT_EXTERN_TEMPLATE`
/// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// Suppose that we wish to "preinstantiate" `bsl::basic_string` for a given
// character type, say, `char`, on platforms that support `extern template`.
// To accomplish this, we would do the following in the `.h` and `.cpp` files
// of the `bslstl_string` component:
// ```
// // bslstl_string.h
// // ...
// #ifdef BSLS_COMPILERFEATURES_SUPPORT_EXTERN_TEMPLATE
// extern template class bsl::String_Imp<char, bsl::string::size_type>;
// extern template class bsl::basic_string<char>;
// #endif
// // ...
//
// // bslstl_string.cpp
// // ...
// #ifdef BSLS_COMPILERFEATURES_SUPPORT_EXTERN_TEMPLATE
// template class bsl::String_Imp<char, bsl::string::size_type>;
// template class bsl::basic_string<char>;
// #endif
// // ...
// ```
//
///Example 2: `__LINE__` Macro Multi-line Value Differences Demonstration
/// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// Note that this isn't an example of use, it is a demonstration of compiler
// preprocessor behavior and the `BSLS_COMPILERFEATURES_PP_LINE_IS_ON_FIRST`
// macro.
//
// Sometimes we write code that uses line numbers for logging or other
// purposes.  Although most of the time the precise values of those line
// numbers (in program output, such as assertions, or logs) is unimportant
// (the output is read by humans who are good at finding the line that
// actually emitted the text), sometimes programs read other programs' output.
// In such cases the precise values for the line numbers may matter.  This
// example demonstrates the two ways our currently supported C++ compilers
// generate line numbers in multi-line macro expansion contexts (from the
// `__LINE__` macro), and how the presence (or absence) of the macro
// `BSLS_COMPILERFEATURES_PP_LINE_IS_ON_FIRST` indicates which method the
// current compiler uses.  First, we define a macro that uses `__LINE__` in its
// replacement text:
// ```
//   #define THATS_MY_LINE(dummy) __LINE__
// ```
// Note that this macro has the function-like syntax so we can easily span its
// invocation to multiple lines.
//
// Next, we record the current line number in a constant, and also record the
// line number from our macro, but we span the macro invocation multiple lines
// to invoke the unspecified behavior.
//
// The two lines must follow each other due to working with line numbering:
// ```
//   const long A_LINE = __LINE__;
//   const long LINE_FROM_MACRO = THATS_MY_LINE
//       (
//           "dummy"
//       )
// .       ;
// ```
// We deliberately extended the macro invocation to more than 2 physical source
// code lines so that we can demonstrate the two distinct behaviors: using the
// line number of the first character or the last.  Extending the number of
// lines *beyond* the macro invocation (by placing the semicolon on its own
// line) has no effect on the line number substitution inside the macro.  The
// dummy argument is required for C++03 compatibility.
//
// If we follow the definition of `A_LINE` without any intervening empty lines
// the line number of the first character of the macro invocation will be
// `A_LINE + 1`, while the last falls on line `A_LINE + 4`.
//
// Now we demonstrate the two different behaviors and how the presence of
// `BSLS_COMPILERFEATURES_PP_LINE_IS_ON_FIRST` indicates which one will occur:
// ```
//   #ifdef BSLS_COMPILERFEATURES_PP_LINE_IS_ON_FIRST
//       assert(A_LINE + 1 == LINE_FROM_MACRO);
//   #else
//       assert(A_LINE + 4 == LINE_FROM_MACRO);
//   #endif
// ```
// Finally note that WG14 N2322 defines this behavior as *unspecified*,
// therefore it is in the realm of possibilities, although not likely (in C++
// compilers) that further, more complicated or even indeterminate behaviors
// may arise.
//
///Bugs in Compilers
///-----------------
//
///`BSLS_COMPILERFEATURES_INITIALIZER_LIST_LEAKS_ON_EXCEPTIONS`
/// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler leaks temporary objects constructed
// trying to initialize a `std::initializer_list` object in the event that one
// of the elements of the list throws from its constructor.
//
// * Compilers affected:
//   - GCC
//   - Oracle CC 12.6
//
///Feature Support in Compilers
///----------------------------
//
// Note that https://en.cppreference.com/w/cpp/compiler_support is a useful
// reference for initial versions to test for support for various features.
//
///`BSLS_COMPILERFEATURES_FULL_CPP11`
/// - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports all the syntax specified by
// the C++11 standard.
//
// * Compiler support:
//   - GCC 5.1
//   - Clang 3.3
//   - Visual Studio 2017 version 14.0 (<u>MSC</u>VER 1900)
//
///`BSLS_COMPILERFEATURES_FULL_CPP14`
/// - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports all the syntax specified by
// the C++14 standard.
//
// * Compiler support:
//   - GCC 6.1
//   - Clang 3.4*
//   - Visual Studio 2017 version 15.3 (<u>MSC</u>VER 1911)
//
// Note that Clang does not support sized deallocation operators (N3778) until
// release 19.1.
//
///`BSLS_COMPILERFEATURES_FULL_CPP17`
/// - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports all the syntax specified by
// the C++17 standard.
//
// * Compiler support:
//   - GCC 9.1
//   - Clang 7.0*
//   - Visual Studio 2019 version 16.1 (<u>MSC</u>VER 1921)
//
// Note that Clang does not support sized deallocation operators (N3778) until
// release 19.1.
//
///`BSLS_COMPILERFEATURES_FULL_CPP20`
/// - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports all the syntax specified by
// the C++20 standard.
//
// * THIS MACRO IS NOT YET DEFINED FOR ANY PLATFORM *
//
///`BSLS_COMPILERFEATURES_PP_LINE_IS_ON_FIRST`
///- - - - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler substitutes the `__LINE__` macro in
// macro expansions with the line number of the first character of the macro
// invocation, which is the recommended practice for the C preprocessor (see
// WG14 N2322 at http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2322.htm).
// Note that all BDE supported compilers that do not define this macro use the
// line number of the last character of the macro invocation instead.
//
// * Compilers that implement N2322 Recommended practice:
//   - GCC 9.0 and later
//
///`BSLS_COMPILERFEATURES_SUPPORT_ALIAS_TEMPLATES`
///- - - - - - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports syntax to introduce a
// `typedef`-name using alias-declaration syntax, declaring a name for a family
// of types.
//
// * Compiler support:
//   - GCC 4.7
//   - Clang 3.0
//   - Visual Studio 2013 version 12.0 (<u>MSC</u>VER 1800)
//   - Oracle CC 12.4
//
///`BSLS_COMPILERFEATURES_SUPPORT_ALIGNAS`
///- - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports the `alignas` alignment
// specifier.
//
// * Compiler support:
//   - GCC 4.8
//   - Clang 3.0
//
// This feature is not yet supported in Visual Studio, IBM xlC, Oracle CC.
//
///`BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_NORETURN`
/// - - - - - - - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports `[[noreturn]]` C++11
// attribute syntax.  MSVC supports the attribute with alternative syntax
// __declspec(noreturn), earlier versions of GCC and Clang support the
// alternative syntax `__attribute__((noreturn))`, and xlC supports the
// alternative syntax `_Noreturn`.  This macro does not support alternative
// syntaxes.
//
// * Compiler support:
//   - GCC 4.8
//   - Clang 3.3
//   - Visual Studio 2015 (<u>MSC</u>VER 1900)
//   - Oracle CC 12.4
//
///`BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_NODISCARD`
/// - - - - - - - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports `[[nodiscard]]` C++17
// attribute syntax.
//
// * Compiler support:
//   - Visual Studio 2017 version 15.3 (<u>MSC</u>VER 1911)
//
///`BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_FALLTHROUGH`
/// - - - - - - - - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports `[[fallthrough]]` C++17
// attribute syntax.
//
// * Compiler support:
//   - GCC 7.3
//   - Clang 3.3
//   - Visual Studio 2017 version 15.0 (<u>MSC</u>VER 1910)
//
///`BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_MAYBE_UNUSED`
/// - - - - - - - - - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports `[[maybe_unused]]` C++17
// attribute syntax.
//
// * Compiler support:
//   - GCC 4.8
//   - Clang 3.3
//   - Visual Studio 2017 version 15.3 (<u>MSC</u>VER 1911)
//
///`BSLS_COMPILERFEATURES_SUPPORT_CONCEPTS`
///- - - - - - - - - - - - - - - - - - - -
// This macro is defined if the Concepts core language feature is fully
// supported, as defined by ISO C++20.
//
// This macro is defined if the standard `__cpp_concepts` feature-test macro
// has at least `202002L` value.
//
// * Compiler support:
//   - GCC 12.1
//   - Visual Studio 2022 version 17.2.2 (`_MSC_VER` 1932)
//   - Clang 19.1
//
///`BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR`
///- - - - - - - - - - - - - - - - - - - - -
// This macro is defined in the compiler supports the `constexpr` reserved
// keyword.
//
// * Compiler support:
//   - GCC 4.7
//   - Clang 3.1
//   - Visual Studio 2017 version 15.0 (<u>MSC</u>VER 1910)
//   - IBM xlC 13
//   - Oracle CC 12.4
//
///`BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR_CPP14`
///- - - - - - - - - - - - - - - - - - - - - - - -
// This macro is defined in the compiler supports the `constexpr` reserved
// keyword with C++14 semantics.
//
// * Compiler support:
//   - gcc 6
//   - clang 3.4
//   - Visual Studio 2017 version 15.0 (<u>MSC</u>VER 1910)
//
///`BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR_CPP17`
///- - - - - - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports the `constexpr` reserved
// keyword with C++17 semantics.
//
// * Compiler support:
//   - gcc 7.3
//   - clang 5
//   - Visual Studio 2017 version 15.0 (<u>MSC</u>VER 1910)
//
///`BSLS_COMPILERFEATURES_SUPPORT_COROUTINE`
///- - - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports at least the C++20 coroutine
// core language features and also provides the `<coroutine>` standard header
// providing the basic library facilities necessary to make use of coroutines.
//
// * Compiler support (in C++20 mode):
//   - gcc 11.1
//   - clang 14
//   - Visual Studio 2019 version 16.11 (<u>MSC</u>VER 1929)
//
///`BSLS_COMPILERFEATURES_SUPPORT_DECLTYPE`
/// - - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports the `decltype` reserved word.
//
// * Compiler support:
//   - GCC 4.3
//   - Clang 3.3
//   - Visual Studio 2010 version 10.0 (<u>MSC</u>VER 1600)
//   - IBM xlC 11.1
//   - Oracle CC 12.4
//
///`BSLS_COMPILERFEATURES_SUPPORT_DEFAULT_TEMPLATE_ARGS`
///- - - - - - - - - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports syntax to introduce defaulted
// functions.
//
// * Compiler support:
//   - GCC 4.3
//   - Clang 2.9
//   - Visual Studio 2013 version 12.0 (<u>MSC</u>VER 1800)
//   - IBM xlC not supported?
//   - Oracle CC 12.4
//
///`BSLS_COMPILERFEATURES_SUPPORT_DEFAULTED_FUNCTIONS`
///- - - - - - - - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports syntax to introduce defaulted
// functions.
//
// * Compiler support:
//   - GCC 4.4
//   - Clang 2.9
//   - Visual Studio 2013 version 12.0 (<u>MSC</u>VER 1800)
//   - IBM xlC 13.1
//   - Oracle CC 12.4
//
///`BSLS_COMPILERFEATURES_SUPPORT_DELETED_FUNCTIONS`
///- - - - - - - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports syntax to introduce deleted
// functions.
//
// * Compiler support:
//   - GCC 4.4
//   - Clang 2.9
//   - Visual Studio 2013 version 12.0 (<u>MSC</u>VER 1800)
//   - IBM xlC 13.1
//   - Oracle CC 12.4
//
///`BSLS_COMPILERFEATURES_SUPPORT_ENUM_CLASS`
///- - - - - - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports strongly typed enumerations
// declared with `enum class`.
//
// * Compiler support:
//   - GCC 4.4
//   - Clang (any)
//   - Visual Studio 2012 version 11.0 (<u>MSC</u>VER 1700)
//
///`BSLS_COMPILERFEATURES_SUPPORT_EXTERN_TEMPLATE`
///- - - - - - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports allowing suppression of
// implicit instantiation of templates by prefixing an explicit instantiation
// directive with the `extern` keyword.
//
// * Compiler support:
//   - GCC 3.3
//   - Clang (any)
//   - Visual Studio 2010 version 10.0 (<u>MSC</u>VER 1600)
//   - IBM xlC 11.1
//   - Oracle CC 12.4
//
///`BSLS_COMPILERFEATURES_SUPPORT_FINAL`
///- - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports both finalizing a class using
// the `final` keyword after the class name as well as preventing further
// derived classes from overriding a `virtual` function by using `final` after
// its signature.
//
// * Compiler support:
//   - GCC 4.7
//   - Clang 3.0
//   - Visual Studio 2012 version 11.0 (<u>MSC</u>VER 1700)
//   - IBM xlC 11.1
//   - Oracle CC 12.4
//
///`BSLS_COMPILERFEATURES_SUPPORT_GENERALIZED_INITIALIZERS`
/// - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports generalized initializers.
//
// * Compiler support:
//   - GCC 4.4
//   - Clang 3.1
//   - Visual Studio 2013 version 12.0 (<u>MSC</u>VER 1800)
//   - IBM xlC not supported
//   - Oracle CC 13
//
///`BSLS_COMPILERFEATURES_SUPPORT_HAS_INCLUDE`
///- - - - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports `__has_include` semantics as
// defined in the C++17 Standard (see also P006R1).  Note that this
// preprocessor feature is often available in earlier language dialects.
//
// * Compiler support:
//   - GCC 5.0
//   - clang (any)
//   - Visual Studio 2017 version 15.3 (<u>MSC</u>VER 1911)
//
///`BSLS_COMPILERFEATURES_SUPPORT_INCLUDE_NEXT`
/// - - - - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports #include_next.
//
// * Compiler support:
//   - GCC (any)
//   - Clang (any)
//   - IBM xlC 8
//   - Oracle CC 12.4
//
///`BSLS_COMPILERFEATURES_SUPPORT_INLINE_NAMESPACE`
/// - - - - - - - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports `inline` namespaces
// introduced in the C++11 Standard.
//
// * Compiler support:
//   - GCC 4.4
//   - Clang 2.9
//   - Visual Studio 2015 version 14.0 (<u>MSC</u>VER 1900)
//   - IBM xlC 11.1
//   - Oracle CC 12.4
//
///`BSLS_COMPILERFEATURES_SUPPORT_INLINE_VARIABLES`
/// - - - - - - - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports `inline` variables introduced
// in the C++17 Standard.
//
// * Compiler support:
//   - GCC 7.0
//   - Clang 3.9
//   - Visual Studio 2017 version 15.5 (<u>MSC</u>VER 1912)
//
///`BSLS_COMPILERFEATURES_SUPPORT_NOEXCEPT`
/// - - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports the `noexcept` reserved
// keyword.
//
// * Compiler support:
//   - GCC 4.6
//   - Clang 3.0
//   - Visual Studio 2015 version 14.0 (<u>MSC</u>VER 1900)
//
///`BSLS_COMPILERFEATURES_SUPPORT_NULLPTR`
///- - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports the `nullptr` reserved word.
//
// * Compiler support:
//   - GCC 4.6
//   - Clang 3.0
//   - Visual Studio 2010 version 10.0 (<u>MSC</u>VER 1600)
//   - IBM xlC 13.1
//   - Oracle CC 12.4
//
///`BSLS_COMPILERFEATURES_SUPPORT_OPERATOR_EXPLICIT`
///- - - - - - - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports use of the `explicit` keyword
// to indicate that a conversion operator only available for explicit
// conversions.
//
// * Compiler support:
//   - GCC 4.5
//   - Clang 3.0
//   - Visual Studio 2013 version 12.0 (<u>MSC</u>VER 1800)
//   - IBM xlC 11.1
//   - Oracle CC 12.4
//
///`BSLS_COMPILERFEATURES_SUPPORT_OVERRIDE`
/// - - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports use of the `override` keyword
// to indicate that a member function is meant to override a `virtual` function
// (and cause a failure if that is not the case).
//
// * Compiler support:
//   - GCC 4.7
//   - Clang 3.0
//   - Visual Studio 2012 version 11.0 (<u>MSC</u>VER 1700)
//   - IBM xlC 11.1
//   - Oracle CC 12.4
//
///`BSLS_COMPILERFEATURES_SUPPORT_RAW_STRINGS`
///- - - - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports the use of C++11-style
// R"tag(string)tag" strings.
//
// * Compiler support:
//   - GCC 4.5
//   - Clang 3.3
//   - Visual Studio 2013 version 12.0 (<u>MSC</u>VER 1800)
//   - xlC 13.1.3 (Not yet supported by this component)
//   - Oracle CC 12.4
//
///`BSLS_COMPILERFEATURES_SUPPORT_REF_QUALIFIERS`
///- - - - - - - - - - - - - - - - - - - - - - - - -
// This macro is defined if member functions with trailing reference qualifiers
// (e.g., `void myfunc(int) &`) and rvalue reference qualifiers (e.g.,
// `void myFunc(int) &&`) are supported.  Note that this macro implies that
// `BSLS_COMPILERFEATURES_SUPPORT_RVALUE_REFERENCES` is also defined.
//
// * Compiler support:
//   - gcc 4.5 (rvalue references v2.1; original draft support in gcc 4.3 is
//     not correct with respect to final spec (v3.0))
//   - clang 2.9
//   - Visual Studio 2015 version 14.0 (<u>MSC</u>VER 1900)
//   - xlC 12.1
//   - Oracle CC 12.4
//
///`BSLS_COMPILERFEATURES_SUPPORT_RVALUE_REFERENCES`
///- - - - - - - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports rvalue references and move
// semantics compatible with the final C++11 specification.  (Semantics have
// changed since early draft proposals.)
//
// * Compiler support:
//   - GCC 4.5 (rvalue references v2.1; original draft support in GCC 4.3 is
//     not correct with respect to final spec (v3.0))
//   - Clang 2.9
//   - Visual Studio 2010 version 10.0 (<u>MSC</u>VER 1600)
//   - IBM xlC 12.1
//   - Oracle CC 12.4
//
///`BSLS_COMPILERFEATURES_SUPPORT_STATIC_ASSERT`
///- - - - - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports the `static_assert` reserved
// word.
//
// * Compiler support:
//   - GCC 4.3
//   - Clang 2.9
//   - Visual Studio 2010 version 10.0 (<u>MSC</u>VER 1600)
//   - IBM xlC 11.1
//   - Oracle CC 12.4
//
//
///`BSLS_COMPILERFEATURES_SUPPORT_STATIC_CALL_OPERATOR`
/// - - - - - - - - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports `static` declarations of
// the function call operator, i.e., `static operator()(parameter-list)`.
// This feture is typically enabled for C++23 and later.
//
// * Compiler support:
//   - GCC 13.1
//   - Clang 16.0
//   - Visual Studio 2022 version 17.14 (<u>MSC</u>VER 1944)
//
///`BSLS_COMPILERFEATURES_SUPPORT_THREE_WAY_COMPARISON`
/// - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports `<=>` operator.
//
// * Compiler support:
//   - GCC 10.1
//   - Clang 11.0
//   - Visual Studio 2019 version 16.11 (<u>MSC</u>VER 1929)
//
///`BSLS_COMPILERFEATURES_SUPPORT_VARIADIC_TEMPLATES`
/// - - - - - - - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports the ability to express a
// template that accepts an arbitrary number of parameters in a type-safe
// manner.
//
// * Compiler support:
//   - GCC 4.3
//   - Clang 2.9
//   - Visual Studio 2015 version 14.0 (<u>MSC</u>VER 1900)
//   - IBM xlC 11.1
//   - Oracle CC 12.4
//
///`BSLS_COMPILERFEATURES_SUPPORT_VARIABLE_TEMPLATES`
/// - - - - - - - - - - - - - - - - - - - - - - - - -
// This macro is defined if the compiler supports variable templates introduced
// in the C++14 Standard.
//
// * Compiler support:
//   - gcc 5.0
//   - clang 3.4
//   - Visual Studio 2015 version 14.0 (<u>MSC</u>VER 1900)
//   - Oracle CC 12.4
//
/// Microsoft Visual Studio versions mapping
///-----------------------------------------
// Microsoft Visual C++ in Microsoft Visual Studio has *many* different
// associated versions:
//
// * Microsoft Visual Studio release name (such as 2015, 2019, 2022 etc.)
// * Microsoft Visual Studio update number (such as Update 6)
// * Microsoft Visual Studio version number (such as 15.6.1)
// * Microsoft Visual C++ Toolset version number (such as 14.30)
// * C++ compiler version number and `_MSVC_VER` (such as 19.32 and 1932)
// * C++ compiler `_MSVC_FULL_VER` (such as 193231329)
//
// The following table shows the mapping between the different version numbers.
// The source for the table was
//: https://dev.to/yumetodo/list-of-mscver-and-mscfullver-8nd
// and the `_MSC_VER` entry on
//: https://learn.microsoft.com/en-us/cpp/preprocessor/predefined-macros
// at 2020-12-13 20:00-05:00 (EST/New York).
//
// ```
// +-------------------+----------+---------+----------+---------------+
// | Visual Studio name & version | Toolset | _MSC_VER | _MSC_FULL_VER |
// +===================+==========+=========+==========+===============+
// | 2015              | 14.0     | 14.0    | 1900     |  190023026    |
// | 2015 Update 1     | 14.0     | 14.0    | 1900     |  190023506    |
// | 2015 Update 2     | 14.0     | 14.0    | 1900     |  190023918    |
// | 2015 Update 3     | 14.0     | 14.0    | 1900     |  190024210    |
// +-------------------+----------+---------+----------+---------------+
// | 2017              | 15.0     | 14.10   | 1910     |  191025017    |
// | 2017 Update 1     | 15.1     | 14.10   | 1910     |  191025017    |
// | 2017 Update 2     | 15.2     | 14.10   | 1910     |  191025017    |
// | 2017 Update 3     | 15.3.3   | 14.11   | 1911     |  191125507    |
// | 2017 Update 4     | 15.4.4   | 14.11   | 1911     |  191125542    |
// |      Update 4(*)  | 15.4.5   | 14.11   | 1911     |  191125547    |
// | 2017 Update 5     | 15.5.2   | 14.12   | 1912     |  191225831    |
// |      Update 5(*)  | 15.5.3   | 14.12   | 1912     |  191225834    |
// |      Update 5(*)  | 15.5.4   | 14.12   | 1912     |  191225834    |
// |      Update 5(*)  | 15.5.6   | 14.12   | 1912     |  191225835    |
// |      Update 5(*)  | 15.5.7   | 14.12   | 1912     |  191225835    |
// | 2017 Update 6     | 15.6.0   | 14.13   | 1913     |  191326128    |
// |      Update 6(*)  | 15.6.1   | 14.13   | 1913     |  191326128    |
// |      Update 6(*)  | 15.6.2   | 14.13   | 1913     |  191326128    |
// |      Update 6(*)  | 15.6.3   | 14.13   | 1913     |  191326129    |
// |      Update 6(*)  | 15.6.4   | 14.13   | 1913     |  191326129    |
// |      Update 6(*)  | 15.6.6   | 14.13   | 1913     |  191326131    |
// |      Update 6(*)  | 15.6.7   | 14.13   | 1913     |  191326132    |
// | 2017 Update 7     | 15.7.1   | 14.14   | 1914     |  191426428    |
// |      Update 7(*)  | 15.7.2   | 14.14   | 1914     |  191426429    |
// |      Update 7(*)  | 15.7.3   | 14.14   | 1914     |  191426430    |
// |      Update 7(*)  | 15.7.5   | 14.14   | 1914     |  191426433    |
// | 2017 Update 8     | 15.8.0   | 14.15   | 1915     |      ?        |
// | 2017 Update 9     | 15.9.0   | 14.16   | 1916     |      ?        |
// |      Update 9(*)  | 15.9.1   | 14.16   | 1916     |  191627023    |
// |      Update 9(*)  | 15.9.4   | 14.16   | 1916     |  191627025    |
// |      Update 9(*)  | 15.9.5   | 14.16   | 1916     |  191627026    |
// |      Update 9(*)  | 15.9.7   | 14.16   | 1916     |  191627027    |
// |      Update 9(*)  | 15.9.11  | 14.16   | 1916     |  191627030    |
// +-------------------+----------+---------+----------+---------------+
// | 2019              | 16.0     | 14.20   | 1920     |  192027508    |
// | 2019 Update  1    | 16.1.2   | 14.21   | 1921     |  192127702    |
// | 2019 Update  2    | 16.2.3   | 14.21   | 1922     |  192227905    |
// | 2019 Update  3    | 16.3.2   | 14.21   | 1923     |  192328105    |
// | 2019 Update  4    | 16.4.0   | 14.24   | 1924     |  192428314    |
// | 2019 Update  5    | 16.5.1   | 14.25   | 1925     |  192528611    |
// | 2019 Update  6    | 16.6.2   | 14.26   | 1926     |  192628806    |
// | 2019 Update  7    | 16.7     | 14.27   | 1927     |  192729112    |
// | 2019 Update  8    | 16.8.1   | 14.28   | 1928     |  192829333    |
// |      Update  8(*) | 16.8.2   | 14.28   | 1928     |  192829334    |
// | 2019 Update  9    | 16.9.2   | 14.28   | 1928     |  192829913    |
// | 2019 Update 11    | 16.11.2  | 14.28   | 1929     |  192930133    |
// +-------------------+----------+---------+----------+---------------+
// | 2022              | 17.0.1   | 14.30   | 1930     |  193030705    |
// | 2022(*)           | 17.0.2   | 14.30   | 1930     |  193030706    |
// | 2022(*)           | 17.2.2   | 14.30   | 1932     |  193231329    |
// | 2022(*)           | 17.3.4   | 14.30   | 1933     |  193331630    |
// +-------------------+----------+---------+----------+---------------+
// ```
// (*) Visual Studio may receive interim updates that do not contribute into
//     the Visual Studio "human friendly" version, but are visible in other
//     version numbers.
//
// ```
//    ####################################################################
//  ########################################################################
// ##                                                                      ##
// ##             THIS HEADER FILE HAS SPECIAL FORMATTING RULES!             ##
// ##            ************************************************            ##
// ##                                                                        ##
// ##  Please follow the rules when updating it.  For specific reasons and   ##
// ##  details please see {Special Formatting Rules and Allowances} above.   ##
// ##                                                                      ##
//  ########################################################################
//    ####################################################################
// ```

#include <bsls_platform.h>
#include <bsls_macrorepeat.h>

#ifdef __has_include
  #if __has_include(<version>)
    #include <version>
  #endif
#endif

// ============================================================================
//         VERIFY COMPILER VERSION SUPPORT FOR REQUESTED ISO LANGUAGE
// ============================================================================

#ifndef BDE_BUILD_SKIP_VERSION_CHECKS

  // Some level of C++20 is enabled, let's verify the compiler is supported
  #if __cplusplus > 201703L || (defined(_MSVC_LANG) && _MSVC_LANG > 201703L)
    #if defined(BSLS_PLATFORM_CMP_GNU) && BSLS_PLATFORM_CMP_VERSION < 110100
      static_assert(0, "At least version 11.1 is required for C++20 support "
          "in GNU CC g++.  This check can be disabled by defining the "
          "'BDE_BUILD_SKIP_VERSION_CHECKS' build flag.");
    #endif  // Too old gcc for C++20

    #if defined(BSLS_PLATFORM_CMP_CLANG) && BSLS_PLATFORM_CMP_VERSION < 150000
      static_assert(0, "At least version 15.0 is required for C++20 support "
          "in LLVM clang.  This check can be disabled by defining the "
          "'BDE_BUILD_SKIP_VERSION_CHECKS' build flag.");
    #endif  // Too old clang for C++20

    #if defined(BSLS_PLATFORM_CMP_MSVC) && BSLS_PLATFORM_CMP_VERSION < 1930
      static_assert(0, "At least version 19.30 is required for C++20 support "
          "in MS Visual C++ (MS Visual Studio 2022).  This check can be "
          "disabled by defining build flag 'BDE_BUILD_SKIP_VERSION_CHECKS'.");
    #endif  // Too old MSVC for C++20

    #if defined(BSLS_PLATFORM_CMP_IBM) || defined(BSLS_PLATFORM_CMP_SUN)
      #error "This compiler does not support C++20.  This check can be "      \
             "disabled by defining the 'BDE_BUILD_SKIP_VERSION_CHECKS' build "\
             "flag.  See also "                                               \
"http://bloomberg.github.io/bde/library_information/supported_platforms.html "\
             "for all compiler and other platform requirements."
      BSLS_PLATFORM_COMPILER_ERROR;
    #endif  // No C++20 on big iron
  #endif  // C++20 features requested
#endif  // ifndef BDE_BUILD_SKIP_VERSION_CHECKS

// ============================================================================
//                      UNIVERSAL MACRO DEFINITIONS
// ============================================================================

#if defined(__cplusplus)
  #define BSLS_COMPILERFEATURES_CPLUSPLUS __cplusplus
#else
  #define BSLS_COMPILERFEATURES_CPLUSPLUS 199711L
#endif

// First, define feature macros for any C++98 features that should be available
// on all compilers, until removed by a later standard.  These macros will be
// specifically undefined when compilers stop supporting that feature in a
// modern build mode.
#define BSLS_COMPILERFEATURES_SUPPORT_THROW_SPECIFICATIONS                    1

// Use the standard compiler-independent feature-test macros (SD-6) for
// compilers that support them.  This support will be mandated by C++20, and it
// is expected that, at some point, future compilers will need only these
// universal definitions, and the platform-specific detection below will need
// no further maintenance.
#if defined(__cpp_guaranteed_copy_elision)
  #define BSLS_COMPILERFEATURES_GUARANTEED_COPY_ELISION                       1
#endif

#if defined(__cpp_unicode_characters) && defined(__cpp_unicode_literals)
  #define BSLS_COMPILERFEATURES_SUPPORT_UNICODE_CHAR_TYPES                    1
#endif

#if defined(__cpp_char8_t)
  #define BSLS_COMPILERFEATURES_SUPPORT_UTF8_CHAR_TYPE                        1
#endif

#if defined(__cpp_hex_float)
  #define BSLS_COMPILERFEATURES_SUPPORT_HEXFLOAT_LITERALS                     1
#endif

#if defined(__cpp_impl_coroutine) && __cpp_impl_coroutine >= 201902L
    // && defined(__cpp_lib_coroutine)  && __cpp_lib_coroutine >= 201902L
    //
    // There are no known compilers that define the core language feature macro
    // but do not provide the corresponding library header.  As *this* header
    // is included into almost every translation unit we won't
    // '#include <coroutine>' or the '<version>' standard headers (that would
    // '#define __cpp_lib_coroutine'), but we verify the presence and value of
    // '__cpp_lib_coroutine' both in the implementation file and the test
    // driver.
    #define BSLS_COMPILERFEATURES_SUPPORT_COROUTINE                           1
#endif

#if defined(__cpp_deduction_guides) && __cpp_deduction_guides >= 201611
  #define BSLS_COMPILERFEATURES_SUPPORT_CTAD                                  1
#endif

#if defined(__cpp_concepts) && __cpp_concepts >= 202002L
  #define BSLS_COMPILERFEATURES_SUPPORT_CONCEPTS                              1
#endif

#if defined(__cpp_static_call_operator) &&                                    \
                                          __cpp_static_call_operator >= 202207L
  #define BSLS_COMPILERFEATURES_SUPPORT_STATIC_CALL_OPERATOR                  1
#endif

#if defined(__cpp_lib_hardware_interference_size) &&                          \
            __cpp_lib_hardware_interference_size >= 201703L
  #define BSLS_COMPILERFEATURES_SUPPORT_HARDWARE_INTERFERENCE                 1
#endif

// Define BDE named macros for more capable evolutions of existing features
// that require testing multiple macros and values.

#if __cplusplus > 201703L || (defined(_MSVC_LANG) && _MSVC_LANG > 201703L)
  // We test against 201907L instead of the published 202002L.
  #if defined(__cpp_constexpr) && __cpp_constexpr >= 201907L
    #if defined(__cpp_constexpr_dynamic_alloc) &&                             \
                                       __cpp_constexpr_dynamic_alloc >= 201907L
      #define BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR_CPP20                   1
    #endif
  #endif
  #if defined(__cpp_consteval) && __cpp_consteval >= 201811L
      #define BSLS_COMPILERFEATURES_SUPPORT_CONSTEVAL_CPP20                   1
  #endif
#endif

// The following feaure support macros have additional dependencies on library
// feature support in the `<version>` header.

#if defined(__cpp_impl_three_way_comparison) &&                               \
                                     __cpp_impl_three_way_comparison >= 201907L
  #if defined(__cpp_lib_three_way_comparison) &&                              \
                                      __cpp_lib_three_way_comparison >= 201907L
    #define BSLS_COMPILERFEATURES_SUPPORT_THREE_WAY_COMPARISON                1
  #endif
#endif

// ============================================================================
//                           ATTRIBUTE DETECTION
// ============================================================================

#if (__cplusplus >= 201103L) && defined(__has_cpp_attribute)

  #if __has_cpp_attribute(fallthrough)
    #define BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_FALLTHROUGH               1
  #endif

  #if __has_cpp_attribute(noreturn)
    #define BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_NORETURN                  1
  #endif

  #if __has_cpp_attribute(nodiscard)
    #define BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_NODISCARD                 1
  #endif

  #if __has_cpp_attribute(maybe_unused)
    #define BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_MAYBE_UNUSED              1
  #endif

#endif

// ============================================================================
//         PLATFORM SPECIFIC FEATURE DETECTION AND MACRO DEFINITIONS
// ============================================================================

// ============================================================================
//                  GNU Compiler Collection / gcc and g++
// ============================================================================

//GCC
//  https://wiki.apache.org/stdcxx/C%2B%2B0xCompilerSupport
// As GCC tracked the evolving C++11 standard, earlier versions of the compiler
// have implementations of earlier specifications of features that can show up
// as bugs compared to the final standard.  Therefore, BDE does not attempt to
// support C++11 in GCC compilers prior to the 4.8 release.
#if defined(BSLS_PLATFORM_CMP_GNU)

  #define BSLS_COMPILERFEATURES_SUPPORT_INCLUDE_NEXT                          1

  #if BSLS_PLATFORM_CMP_VERSION >= 30300
    #define BSLS_COMPILERFEATURES_SUPPORT_EXTERN_TEMPLATE                     1
  #endif  // version >= 3.3

  // GCC provides support to the following features, prior to C++17,
  // independent of language dialect.
  #if BSLS_PLATFORM_CMP_VERSION >= 50000

    #ifndef BSLS_COMPILERFEATURES_GUARANTEED_COPY_ELISION
      #define BSLS_COMPILERFEATURES_GUARANTEED_COPY_ELISION                   1
    #endif  // feature test macro may have already defined this

    #define BSLS_COMPILERFEATURES_SUPPORT_HAS_INCLUDE                         1
  #endif  // at least gcc 5.0

  #if BSLS_PLATFORM_CMP_VERSION < 120000
    #define BSLS_COMPILERFEATURES_INITIALIZER_LIST_LEAKS_ON_EXCEPTIONS        1
  #endif  // before gcc 12.0

  #if !defined(__GXX_EXPERIMENTAL_CXX0X__) ||                                \
                            (__cplusplus < 201500 && defined(__STRICT_ANSI__))
    // Supported gcc compilers *always* define '__cpp_hex_float', even if the
    // core language feature is not supported in the current configuration of
    // a build, and they define it to the exact same value ('201603LL')
    // regardless of actual support for literals.  We remedy this by
    // undefining the hexfloat-literal-support macro in those cases when it
    // is not really supported, but gcc said so.  There are 2 such cases:
    //: 1 Language mode is below C++11
    //: 2 Language mode is below C++17 experimental core language support and
    //:   GNU extensions are not enabled.
    //
    // '__GXX_EXPERIMENTAL_CXX0X__' is defined when at least basic C++11
    // features are present (should be used instead of '__cplusplus').
    // g++ defines the '__cplusplus' macro to the non-standard value of
    // 201500 to indicate experimental C++17 support.
    #if defined(BSLS_COMPILERFEATURES_SUPPORT_HEXFLOAT_LITERALS)
      #undef BSLS_COMPILERFEATURES_SUPPORT_HEXFLOAT_LITERALS
    #endif  // '__cpp_hex_float' was defined, but is not supported.
  #endif  // No C++11 or GNU extensions not enabled, C++17 not enabled

  // GCC -std=c++11 or -std=c++0x or -std=gnu++11 or -std=gnu++0x
  #if defined(__GXX_EXPERIMENTAL_CXX0X__)

    #if BSLS_COMPILERFEATURES_CPLUSPLUS < 201103L
      #undef  BSLS_COMPILERFEATURES_CPLUSPLUS
      #define BSLS_COMPILERFEATURES_CPLUSPLUS 201103L
    #endif  // C++ standard date was set to older standard than C++11

    #if BSLS_PLATFORM_CMP_VERSION >= 40800
      #define BSLS_COMPILERFEATURES_SUPPORT_ALIAS_TEMPLATES                   1
      #define BSLS_COMPILERFEATURES_SUPPORT_ALIGNAS                           1
      #define BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_NORETURN                1
         // GCC supports '__attribute__((noreturn))' in earlier versions

      #define BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR                         1
      #define BSLS_COMPILERFEATURES_SUPPORT_DECLTYPE                          1
      #define BSLS_COMPILERFEATURES_SUPPORT_DEFAULT_TEMPLATE_ARGS             1
      #define BSLS_COMPILERFEATURES_SUPPORT_DEFAULTED_FUNCTIONS               1
      #define BSLS_COMPILERFEATURES_SUPPORT_DELETED_FUNCTIONS                 1
      #define BSLS_COMPILERFEATURES_SUPPORT_ENUM_CLASS                        1
      #define BSLS_COMPILERFEATURES_SUPPORT_FINAL                             1
      #define BSLS_COMPILERFEATURES_SUPPORT_GENERALIZED_INITIALIZERS          1
      #define BSLS_COMPILERFEATURES_SUPPORT_INLINE_NAMESPACE                  1
      #define BSLS_COMPILERFEATURES_SUPPORT_NOEXCEPT                          1
      #define BSLS_COMPILERFEATURES_SUPPORT_NULLPTR                           1
      #define BSLS_COMPILERFEATURES_SUPPORT_OPERATOR_EXPLICIT                 1
      #define BSLS_COMPILERFEATURES_SUPPORT_OVERRIDE                          1
      #define BSLS_COMPILERFEATURES_SUPPORT_RAW_STRINGS                       1
      #define BSLS_COMPILERFEATURES_SUPPORT_REF_QUALIFIERS                    1
      #define BSLS_COMPILERFEATURES_SUPPORT_RVALUE_REFERENCES                 1
      #define BSLS_COMPILERFEATURES_SUPPORT_STATIC_ASSERT                     1
      #define BSLS_COMPILERFEATURES_SUPPORT_USER_DEFINED_LITERALS             1
      #define BSLS_COMPILERFEATURES_SUPPORT_VARIADIC_TEMPLATES                1
    #endif  // at least gcc 4.8

    #if BSLS_PLATFORM_CMP_VERSION >= 50000
      #define BSLS_COMPILERFEATURES_SUPPORT_TRAITS_HEADER                     1
        // Note that while basic support is available in earlier versions
        // of the library, the full header is not implemented until gcc 5.0.
     #endif  // at least gcc 5.0
  #endif  // at least C++11

  #if BSLS_PLATFORM_CMP_VERSION >= 90000
    #define BSLS_COMPILERFEATURES_PP_LINE_IS_ON_FIRST                         1
  #endif  // at least gcc 9.0

  #if __cplusplus >= 201402L
    // Don't enable (not fully supported) extended constexpr rules for gcc 5.x.
    // See {DRQS 164511755} for details.
    #if BSLS_PLATFORM_CMP_VERSION >= 60000
      #define BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR_CPP14                   1
    #endif  // at least gcc 6.0

    #define BSLS_COMPILERFEATURES_SUPPORT_VARIABLE_TEMPLATES                  1
  #endif  // at least C++14

  // GCC defines the '__cplusplus' macro to the non-standard value of 201500 to
  // indicate experimental C++17 support.
  #if __cplusplus >= 201500

    #if BSLS_PLATFORM_CMP_VERSION >= 70000
      #define BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_FALLTHROUGH             1
      #define BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_MAYBE_UNUSED            1
      #define BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR_CPP17                   1
      #define BSLS_COMPILERFEATURES_SUPPORT_INLINE_VARIABLES                  1

      #ifndef BSLS_COMPILERFEATURES_SUPPORT_HEXFLOAT_LITERALS
        #define BSLS_COMPILERFEATURES_SUPPORT_HEXFLOAT_LITERALS               1
      #endif  // feature test macro may have already defined this

      // C++98 throw specifications are removed in C++17 mode
      #undef BSLS_COMPILERFEATURES_SUPPORT_THROW_SPECIFICATIONS
    #endif  // at least gcc 7.0

    #if BSLS_PLATFORM_CMP_VERSION >= 70200
      // Early release of gcc 7.0 have a name-mangling bug with 'noexcept' on
      // "abominable" function types.
      #define BSLS_COMPILERFEATURES_SUPPORT_NOEXCEPT_IN_FNC_TYPE              1
    #endif  // at least gcc 7.2
  #endif  // at least experimental C++17 support

  // Define full CPP macros
  #if BSLS_PLATFORM_CMP_VERSION >= 50000
    #if BSLS_COMPILERFEATURES_CPLUSPLUS >= 201103L
      #define BSLS_COMPILERFEATURES_FULL_CPP11                                1
    #endif
  #endif

  #if BSLS_PLATFORM_CMP_VERSION >= 60000
    #if BSLS_COMPILERFEATURES_CPLUSPLUS >= 201402L
      #define BSLS_COMPILERFEATURES_FULL_CPP14                                1
    #endif
  #endif

  #if BSLS_PLATFORM_CMP_VERSION >= 90000
    #if BSLS_COMPILERFEATURES_CPLUSPLUS >= 201703L
      #define BSLS_COMPILERFEATURES_FULL_CPP17                                1
    #endif
  #endif
#endif  // GNU Compiler Collection C++

// ============================================================================
//              LLVM Clang and Apple Clang / clang and clang++
// ============================================================================

//Clang
// http://clang.llvm.org/cxx_status.html
// http://clang.llvm.org/docs/LanguageExtensions.html
#if defined(BSLS_PLATFORM_CMP_CLANG)

  #ifndef BSLS_COMPILERFEATURES_GUARANTEED_COPY_ELISION
    #define BSLS_COMPILERFEATURES_GUARANTEED_COPY_ELISION                     1
  #endif  // feature test macro may have already defined this

  #define BSLS_COMPILERFEATURES_SUPPORT_HAS_INCLUDE                           1

  #ifndef BSLS_COMPILERFEATURES_SUPPORT_HEXFLOAT_LITERALS
    #define BSLS_COMPILERFEATURES_SUPPORT_HEXFLOAT_LITERALS                   1
  #endif  // feature test macro may have already defined this

  #define BSLS_COMPILERFEATURES_SUPPORT_INCLUDE_NEXT                          1
  #define BSLS_COMPILERFEATURES_SUPPORT_EXTERN_TEMPLATE                       1

  // clang -std=c++11 or -std=c++0x or -std=gnu++11 or -std=gnu++0x Clang 2.9
  #if __has_feature(cxx_rvalue_references)
    #define BSLS_COMPILERFEATURES_SUPPORT_RVALUE_REFERENCES                   1
  #endif

  #if __has_feature(cxx_reference_qualified_functions) &&                    \
                                          __has_feature(cxx_rvalue_references)
    #define BSLS_COMPILERFEATURES_SUPPORT_REF_QUALIFIERS                      1
  #endif

  #if __has_feature(cxx_default_function_template_args)
    #define BSLS_COMPILERFEATURES_SUPPORT_DEFAULT_TEMPLATE_ARGS               1
  #endif

  #if __has_feature(cxx_defaulted_functions)
    #define BSLS_COMPILERFEATURES_SUPPORT_DEFAULTED_FUNCTIONS                 1
  #endif

  #if __has_feature(cxx_deleted_functions)
    #define BSLS_COMPILERFEATURES_SUPPORT_DELETED_FUNCTIONS                   1
  #endif

  #if __has_feature(cxx_static_assert)
    #define BSLS_COMPILERFEATURES_SUPPORT_STATIC_ASSERT                       1
  #endif

  #if __has_feature(cxx_inline_namespaces) ||                                \
                                        __has_extension(cxx_inline_namespaces)
    #define BSLS_COMPILERFEATURES_SUPPORT_INLINE_NAMESPACE                    1
  #endif

  #if __has_feature(cxx_variadic_templates)
    #define BSLS_COMPILERFEATURES_SUPPORT_VARIADIC_TEMPLATES                  1
  #endif

  // Clang 3.0
  #if __has_feature(cxx_alias_templates)
    #define BSLS_COMPILERFEATURES_SUPPORT_ALIAS_TEMPLATES                     1
  #endif

  #if __has_feature(cxx_noexcept)
    #define BSLS_COMPILERFEATURES_SUPPORT_NOEXCEPT                            1
  #endif

  #if __has_feature(cxx_raw_string_literals)
    #define BSLS_COMPILERFEATURES_SUPPORT_RAW_STRINGS                         1
  #endif

  // Clang 3.1
  #if __has_feature(cxx_constexpr)
    #define BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR                           1
  #endif

  #if __has_feature(cxx_user_literals)
    #define BSLS_COMPILERFEATURES_SUPPORT_USER_DEFINED_LITERALS               1
  #endif

  // Clang 3.4
  #if __has_feature(cxx_relaxed_constexpr)
    #define BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR_CPP14                     1
  #endif

  #if __has_feature(cxx_explicit_conversions)
    #define BSLS_COMPILERFEATURES_SUPPORT_OPERATOR_EXPLICIT                   1
  #endif

  #if __has_feature(cxx_override_control)
    #define BSLS_COMPILERFEATURES_SUPPORT_FINAL                               1
    #define BSLS_COMPILERFEATURES_SUPPORT_OVERRIDE                            1
  #endif

  #if __has_feature(cxx_nullptr)
    #define BSLS_COMPILERFEATURES_SUPPORT_NULLPTR                             1
  #endif

  // Clang 3.1
  #if __has_feature(cxx_generalized_initializers)
    #define BSLS_COMPILERFEATURES_SUPPORT_GENERALIZED_INITIALIZERS            1
  #endif

  #if __has_feature(cxx_alignas)
    #define BSLS_COMPILERFEATURES_SUPPORT_ALIGNAS                             1
  #endif

  // Clang 3.3
  #if __has_feature(cxx_decltype)
    #define BSLS_COMPILERFEATURES_SUPPORT_DECLTYPE                            1
  #endif

  // Clang 3.4
  #if __has_feature(cxx_variable_templates)
    #define BSLS_COMPILERFEATURES_SUPPORT_VARIABLE_TEMPLATES                  1
  #endif

  #if __has_feature(cxx_attributes)
    #define BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_NORETURN                  1
      // Note that Clang supports __attribute__((noreturn)) in earlier versions
  #endif

  #if BSLS_COMPILERFEATURES_CPLUSPLUS < 201103L &&                           \
                                           defined(__GXX_EXPERIMENTAL_CXX0X__)
    #undef  BSLS_COMPILERFEATURES_CPLUSPLUS
    #define BSLS_COMPILERFEATURES_CPLUSPLUS 201103L
  #endif  // too old standard date fixed up

  #if (__cplusplus >= 201103L)
    #define BSLS_COMPILERFEATURES_SUPPORT_ENUM_CLASS                          1
  #endif

  #if (__cplusplus >= 201103L ||                                              \
      (defined(__GXX_EXPERIMENTAL_CXX0X__) &&                                 \
       defined(__apple_build_version__)))                                     \
      && __has_include(<type_traits>)
    #define BSLS_COMPILERFEATURES_SUPPORT_TRAITS_HEADER                       1
  #endif  // at least C++11 support and has the header

  // works only with --std=c++1z or --std=c++17
  #if __cplusplus >= 201703L  // at least C++17
    #define BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR_CPP17                     1
    #define BSLS_COMPILERFEATURES_SUPPORT_INLINE_VARIABLES                    1
    #define BSLS_COMPILERFEATURES_SUPPORT_NOEXCEPT_IN_FNC_TYPE                1
  #endif  // at least C++17

  // When compiling in >= C++11 mode on a non-Darwin platform, assume that the
  // Clang version is at least 3.0 and accompanied by a GCC toolchain that is
  // at least version 4.8 and which supports clang.
  #if defined(__GXX_EXPERIMENTAL_CXX0X__) &&                                 \
      (!defined(__APPLE_CC__) || __APPLE_CC__ >= 6000)
    #define BSLS_COMPILERFEATURES_SUPPORT_TRAITS_HEADER                       1
  #endif

  // Define full CPP macros
  #if BSLS_PLATFORM_CMP_VERSION >= 30300
    #if BSLS_COMPILERFEATURES_CPLUSPLUS >= 201103L
      #define BSLS_COMPILERFEATURES_FULL_CPP11                                1
    #endif
  #endif

  #if BSLS_PLATFORM_CMP_VERSION >= 30400
    #if BSLS_COMPILERFEATURES_CPLUSPLUS >= 201402L
      #define BSLS_COMPILERFEATURES_FULL_CPP14                                1
    #endif
  #endif

  #if BSLS_PLATFORM_CMP_VERSION >= 70000
    #if BSLS_COMPILERFEATURES_CPLUSPLUS >= 201703L
      #define BSLS_COMPILERFEATURES_FULL_CPP17                                1
    #endif
  #endif

  // clang does not yet follow WG14 N2322 Recommended practice
  // #define BSLS_COMPILERFEATURES_PP_LINE_IS_ON_FIRST
#endif  // Clang

// ============================================================================
//                  Microsoft Visual Studio / MSVC / cl.exe
// ============================================================================

//MSVC (Minimum supported version is MSVC 2015)
// http://msdn.microsoft.com/en-us/library/hh567368.aspx
// http://blogs.msdn.com/b/vcblog/archive/2014/06/11/c-11-14-feature-tables-for-visual-studio-14-ctp1.aspx
#if defined(BSLS_PLATFORM_CMP_MSVC)

// MSVC enables C++11 features automatically in versions that provide the
// feature.  Features can not be disabled.
//
//: * extern template is not supported.  It is documented as being "supported"
//:   but behaves in a non-conforming manner.

  #if BSLS_PLATFORM_CMP_VERSION < 1900
    #error Earliest supported toolset version is 19.0, Visual Studio 2015
    BSLS_PLATFORM_COMPILER_ERROR;
    // Too old compiler, not supported.
  #endif  // Earlier than Visual Studio 2015

  // Not only does Microsoft not always report the language dialect properly in
  // '__cplusplus', many users depends upon it not reflecting the right
  // version, therefore we need to use the Microsoft specific predefined macro
  // '_MSVC_LANG'.  See https://goo.gl/ikfyDw and
  // https://docs.microsoft.com/en-us/cpp/preprocessor/predefined-macros
  // Note that '_MSVC_LANG' is only useful for distinguishing MSVC 2017 from
  // MSVC 2014.
  #undef BSLS_COMPILERFEATURES_CPLUSPLUS
  #if defined(_MSVC_LANG)
    #define BSLS_COMPILERFEATURES_CPLUSPLUS _MSVC_LANG
  #else
    #define BSLS_COMPILERFEATURES_CPLUSPLUS 201103L
  #endif  // _MSVC_LANG

  #undef BSLS_COMPILERFEATURES_SUPPORT_THROW_SPECIFICATIONS
    // MSVC has never properly implemented this feature, even before it was
    // removed by C++17.  It would parse the syntax, but the runtime behavior
    // simply would simply ignore the exception specification.

  // These features are supported in the lowest version of MSVC we support
  #define BSLS_COMPILERFEATURES_SUPPORT_ALIAS_TEMPLATES                       1
  #define BSLS_COMPILERFEATURES_SUPPORT_ALIGNAS                               1
  #define BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_NORETURN                    1
  #define BSLS_COMPILERFEATURES_SUPPORT_DECLTYPE                              1
  #define BSLS_COMPILERFEATURES_SUPPORT_DEFAULT_TEMPLATE_ARGS                 1
  #define BSLS_COMPILERFEATURES_SUPPORT_DEFAULTED_FUNCTIONS                   1
  #define BSLS_COMPILERFEATURES_SUPPORT_DELETED_FUNCTIONS                     1
  #define BSLS_COMPILERFEATURES_SUPPORT_ENUM_CLASS                            1
  #define BSLS_COMPILERFEATURES_SUPPORT_EXTERN_TEMPLATE                       1
  #define BSLS_COMPILERFEATURES_SUPPORT_FINAL                                 1
  #define BSLS_COMPILERFEATURES_SUPPORT_GENERALIZED_INITIALIZERS              1
  #define BSLS_COMPILERFEATURES_SUPPORT_INLINE_NAMESPACE                      1
  #define BSLS_COMPILERFEATURES_SUPPORT_NOEXCEPT                              1
  #define BSLS_COMPILERFEATURES_SUPPORT_NULLPTR                               1
  #define BSLS_COMPILERFEATURES_SUPPORT_OPERATOR_EXPLICIT                     1
  #define BSLS_COMPILERFEATURES_SUPPORT_OVERRIDE                              1
  #define BSLS_COMPILERFEATURES_SUPPORT_RAW_STRINGS                           1
  #define BSLS_COMPILERFEATURES_SUPPORT_REF_QUALIFIERS                        1
  #define BSLS_COMPILERFEATURES_SUPPORT_RVALUE_REFERENCES                     1
  #define BSLS_COMPILERFEATURES_SUPPORT_STATIC_ASSERT                         1
  #define BSLS_COMPILERFEATURES_SUPPORT_TRAITS_HEADER                         1
  #define BSLS_COMPILERFEATURES_SUPPORT_USER_DEFINED_LITERALS                 1
  #define BSLS_COMPILERFEATURES_SUPPORT_VARIADIC_TEMPLATES                    1

  #ifndef BSLS_COMPILERFEATURES_GUARANTEED_COPY_ELISION
    #define BSLS_COMPILERFEATURES_GUARANTEED_COPY_ELISION                     1
  #endif  // feature test macro may have already defined this

  #ifndef BSLS_COMPILERFEATURES_SUPPORT_UNICODE_CHAR_TYPES
    #define BSLS_COMPILERFEATURES_SUPPORT_UNICODE_CHAR_TYPES                  1
  #endif  // feature test macro may have already defined this

  // The variable template C++14 compiler feature is supported since Microsoft
  // Visual Studio 2015 update 2 toolset '_MSC_FULL_VER' 190023918.
  #if _MSC_FULL_VER >= 190023918
    #define BSLS_COMPILERFEATURES_SUPPORT_VARIABLE_TEMPLATES                  1
  #endif  // at least Microsoft Visual Studio 2015 Update 2

  #if BSLS_PLATFORM_CMP_VERSION >= 1910  // Microsoft Visual Studio 2017
    #define BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR                           1
    #define BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR_CPP14                     1

    #if BSLS_COMPILERFEATURES_CPLUSPLUS >= 201703L
      #define BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_FALLTHROUGH             1
      #define BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR_CPP17                   1
    #endif  // at least C++17
  #endif  // at least Microsoft Visual Studio 2017

  // MSVC does not support the non-standard '#include_next' directive
  //#define BSLS_COMPILERFEATURES_SUPPORT_INCLUDE_NEXT

  // MS Visual Studio 2017 Update 4, toolset version 14.11
  #if BSLS_PLATFORM_CMP_VERSION >= 1911
    #define BSLS_COMPILERFEATURES_SUPPORT_HAS_INCLUDE                         1

    #if BSLS_COMPILERFEATURES_CPLUSPLUS >= 201703L
      #define BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_MAYBE_UNUSED            1
      #define BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_NODISCARD               1

      #if !defined(BSLS_COMPILERFEATURES_SUPPORT_HEXFLOAT_LITERALS)
        #define BSLS_COMPILERFEATURES_SUPPORT_HEXFLOAT_LITERALS               1
      #endif  // feature test macro may have already defined this
    #endif  // at least C++17
  #endif  // at least Microsoft Visual Studio 2017, toolset version 14.11

  // MS Visual Studio 2017 Update 5, toolset version 14.12
  #if BSLS_PLATFORM_CMP_VERSION >= 1912
    #if BSLS_COMPILERFEATURES_CPLUSPLUS >= 201703L
      #define BSLS_COMPILERFEATURES_SUPPORT_INLINE_VARIABLES                  1
      #define BSLS_COMPILERFEATURES_SUPPORT_NOEXCEPT_IN_FNC_TYPE              1
    #endif  // at least C++17
  #endif  // at least Microsoft Visual Studio 2017, toolset version 14.12

  #if BSLS_PLATFORM_CMP_VERSION >= 1910 && BSLS_PLATFORM_CMP_VERSION < 1920
    // MSVC2017 crashes when building bsl_deque.h with CTAD enabled.
    #ifdef BSLS_COMPILERFEATURES_SUPPORT_CTAD
      #undef BSLS_COMPILERFEATURES_SUPPORT_CTAD
    #endif
  #endif  // some Microsoft Visual Studio 2017, toolset < 14.20

  // Microsoft Visual Studio 2017
  #if BSLS_PLATFORM_CMP_VERSION >= 1910  // Microsoft Visual Studio 2017
    #if BSLS_COMPILERFEATURES_CPLUSPLUS >= 201103L
      #define BSLS_COMPILERFEATURES_FULL_CPP11                                1
    #endif
  #endif  // at least Microsoft Visual Studio 2019, toolset version 14.21

  // MS Visual Studio 2017 Update 4, toolset version 14.11
  #if BSLS_PLATFORM_CMP_VERSION >= 1911
    #if BSLS_COMPILERFEATURES_CPLUSPLUS >= 201402L
      #define BSLS_COMPILERFEATURES_FULL_CPP14                                1
    #endif
  #endif  // at least Microsoft Visual Studio 2019, toolset version 14.21

  // MS Visual Studio 2019 Update 1, toolset version 14.21
  #if BSLS_PLATFORM_CMP_VERSION >= 1921
    #if BSLS_COMPILERFEATURES_CPLUSPLUS >= 201703L
      #define BSLS_COMPILERFEATURES_FULL_CPP17                                1
    #endif
  #endif  // at least Microsoft Visual Studio 2019, toolset version 14.21

  // Microsoft Visual Studio doesn't follow WG14 N2322 Recommended practice yet
  // #define BSLS_COMPILERFEATURES_PP_LINE_IS_ON_FIRST
#endif  // Microsoft Visual Studio

// ============================================================================
//                          IBM Visual Age / xlC
// ============================================================================

#if defined(BSLS_PLATFORM_CMP_IBM)
// IBM Visual Age xlC 11.1 and better include increasing support for C++11
// http://www-01.ibm.com/support/knowledgecenter/SSGH3R_13.1.0/com.ibm.xlcpp131.aix.doc/compiler_ref/macros_lang_levels.html
// http://www-01.ibm.com/support/knowledgecenter/SSGH3R_13.1.0/com.ibm.xlcpp131.aix.doc/compiler_ref/opt_langlvl.html
//  xlC_r -qlanglvl=extended    (include next, extern template, noreturn)
//  xlC_r -qlanglvl=extended0x  (additional features)

  #if defined(__IBMCPP_CONSTEXPR)
    #define BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR                           1
  #endif

  #if defined(__IBMCPP_DECLTYPE)
    #define BSLS_COMPILERFEATURES_SUPPORT_DECLTYPE                            1
  #endif

  #if defined(__IBMCPP_DEFAULTED_AND_DELETED_FUNCTIONS)
    #define BSLS_COMPILERFEATURES_SUPPORT_DEFAULTED_FUNCTIONS                 1
    #define BSLS_COMPILERFEATURES_SUPPORT_DELETED_FUNCTIONS                   1
  #endif

  #if defined(__IBMCPP_EXPLICIT)
    #define BSLS_COMPILERFEATURES_SUPPORT_OPERATOR_EXPLICIT                   1
  #endif

  #if defined(__IBMCPP_EXTERN_TEMPLATE)
    #define BSLS_COMPILERFEATURES_SUPPORT_EXTERN_TEMPLATE                     1
  #endif

  #if defined(__IBM_INCLUDE_NEXT)
    #define BSLS_COMPILERFEATURES_SUPPORT_INCLUDE_NEXT                        1
  #endif

  #if defined(__IBMCPP_INLINE_NAMESPACE)
    #define BSLS_COMPILERFEATURES_SUPPORT_INLINE_NAMESPACE                    1
  #endif

  #if defined(__IBMCPP_NULLPTR)
    #define BSLS_COMPILERFEATURES_SUPPORT_NULLPTR                             1
  #endif

  #if defined(__IBMCPP_OVERRIDE)
    #define BSLS_COMPILERFEATURES_SUPPORT_FINAL                               1
    #define BSLS_COMPILERFEATURES_SUPPORT_OVERRIDE                            1
  #endif

  #if defined(__IBMCPP_RVALUE_REFERENCES)
    #define BSLS_COMPILERFEATURES_SUPPORT_REF_QUALIFIERS                      1
    #define BSLS_COMPILERFEATURES_SUPPORT_RVALUE_REFERENCES                   1
  #endif

  #if defined(__IBMCPP_STATIC_ASSERT)
    #define BSLS_COMPILERFEATURES_SUPPORT_STATIC_ASSERT                       1
  #endif

  #if defined(__IBMCPP_VARIADIC_TEMPLATES)
    #define BSLS_COMPILERFEATURES_SUPPORT_VARIADIC_TEMPLATES                  1
  #endif

  #if defined(__IBMC_NORETURN)
      // xlC has '_Noreturn', not the standard attribute
      //#define BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_NORETURN
  #endif

  #if defined(__C99_HEX_FLOAT_CONST)
    // Unfortunately xlC does not compile hexadecimal floating point literals
    // properly (at least for the 'double' type that we use most).  Denormal
    // values smaller than '0x0.8000000000000p-1022' are compiled to zero.
    // Hence we undefine this macro unless the compiler is updated (from
    // version 0x1001 where the bug was observed).
    #if BSLS_PLATFORM_CMP_VERSION <= 0x1001
      #ifdef BSLS_COMPILERFEATURES_SUPPORT_HEXFLOAT_LITERALS
        #undef BSLS_COMPILERFEATURES_SUPPORT_HEXFLOAT_LITERALS
      #endif
    #elif !defined(BSLS_COMPILERFEATURES_SUPPORT_HEXFLOAT_LITERALS)
        // The test driver verifies if the offending hexfloat literals now
        // compile to their propers values on this newer compiler version.  If
        // not update the version check above to include this version as well.
      #define BSLS_COMPILERFEATURES_SUPPORT_HEXFLOAT_LITERALS                 1
    #endif  // standard feature test macro may have already defined this
  #endif

  // (not yet supported in xlC)
  //https://www.ibm.com/support/knowledgecenter/SSGH3R_16.1.0/com.ibm.xlcpp161.aix.doc/language_ref/cpp11_support.html
  //
  // #define BSLS_COMPILERFEATURES_SUPPORT_ALIAS_TEMPLATES
  // #define BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR_CPP14
  // #define BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR_CPP17
  // #define BSLS_COMPILERFEATURES_SUPPORT_NOEXCEPT
  // #define BSLS_COMPILERFEATURES_SUPPORT_USER_DEFINED_LITERALS

  // Not yet tested for support
  //
  // #define? BSLS_COMPILERFEATURES_SUPPORT_RAW_STRINGS
  // #define? BSLS_COMPILERFEATURES_SUPPORT_VARIABLE_TEMPLATES

  // Not yet enabling C++17 support, but pro-active test drivers may want to
  // add coverage.
  //
  // #define BSLS_COMPILERFEATURES_SUPPORT_HAS_INCLUDE
  // #define BSLS_COMPILERFEATURES_SUPPORT_INLINE_VARIABLES
  // #define BSLS_COMPILERFEATURES_SUPPORT_NOEXCEPT_IN_FNC_TYPE

  // IBM Visual Age Suite does not yet follow WG14 N2322 Recommended practice
  // #define BSLS_COMPILERFEATURES_PP_LINE_IS_ON_FIRST
#endif  // IBM Visual Age Suite

// ============================================================================
//                       Oracle Developer Studio / CC
// ============================================================================

#if defined(BSLS_PLATFORM_CMP_SUN)
// Oracle Developer Studio 12.4 claims C++11 support except for C++11
// concurrency and atomic operations, and for user-defined literals
// http://docs.oracle.com/cd/E37069_01/html/E37071/gncix.html#scrolltoc
// No C++11 features are available by default.  To use any C++11 features, you
// must use the -std=c++11 option with the CC compiler.
// ('__cplusplus >= 201103L' when Oracle Solaris Studio 'CC -std=c++11' is
// invoked)

  // CC -std=c++11 or later
  #if __cplusplus >= 201103L

    // Oracle Developer Studio 12.4 (CC version 5.13) or newer
    #if BSLS_PLATFORM_CMP_VERSION >= 0x5130
      #define BSLS_COMPILERFEATURES_SUPPORT_ALIAS_TEMPLATES                   1
      #define BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_NORETURN                1
      #define BSLS_COMPILERFEATURES_SUPPORT_DECLTYPE                          1
      #define BSLS_COMPILERFEATURES_SUPPORT_DEFAULTED_FUNCTIONS               1
      #define BSLS_COMPILERFEATURES_SUPPORT_DELETED_FUNCTIONS                 1
      #define BSLS_COMPILERFEATURES_SUPPORT_ENUM_CLASS                        1
      #define BSLS_COMPILERFEATURES_SUPPORT_EXTERN_TEMPLATE                   1
      #define BSLS_COMPILERFEATURES_SUPPORT_FINAL                             1
      #define BSLS_COMPILERFEATURES_SUPPORT_INLINE_NAMESPACE                  1
      #define BSLS_COMPILERFEATURES_SUPPORT_NOEXCEPT                          1
      #define BSLS_COMPILERFEATURES_SUPPORT_NULLPTR                           1
      #define BSLS_COMPILERFEATURES_SUPPORT_OPERATOR_EXPLICIT                 1
      #define BSLS_COMPILERFEATURES_SUPPORT_OVERRIDE                          1
      #define BSLS_COMPILERFEATURES_SUPPORT_RAW_STRINGS                       1
      #define BSLS_COMPILERFEATURES_SUPPORT_STATIC_ASSERT                     1
    #endif  // at least version 5.13

    // Oracle Developer Studio 12.5 (CC version 5.14) or newer
    #if BSLS_PLATFORM_CMP_VERSION >= 0x5140
      #define BSLS_COMPILERFEATURES_SUPPORT_GENERALIZED_INITIALIZERS          1
        // CC 12.4 will overly aggressively match an initializer list when it
        // sees brace initialization, leading to rejection of valid code when
        // there is no valid initializer list conversion, but another method
        // creating a temporary object from the braced arguments should have
        // been chosen.

      #define BSLS_COMPILERFEATURES_SUPPORT_REF_QUALIFIERS                    1
        // Although this feature might be available in an earlier compiler, we
        // are asking for trouble if we don't keep this feature together with
        // rvalue references.

      #define BSLS_COMPILERFEATURES_SUPPORT_RVALUE_REFERENCES                 1
        // CC 12.4 hits an awkward bug when performing deduction in some corner
        // cases, which happen to be important to our vector implementation.

      #define BSLS_COMPILERFEATURES_SUPPORT_TRAITS_HEADER                     1
        // The previous compiler ships with a mostly-complete version of the
        // <type_traits> header, but we insist on a full implementation before
        // defining this macro.

      #define BSLS_COMPILERFEATURES_SUPPORT_VARIADIC_TEMPLATES                1
        // CC 12.4 has problems partially ordering template parameter packs
        // that typically result in failing to compile with ambiguity errors.

      #define BSLS_COMPILERFEATURES_SUPPORT_UNICODE_CHAR_TYPES                1

      #define BSLS_COMPILERFEATURES_SUPPORT_USER_DEFINED_LITERALS             1
        // https://docs.oracle.com/cd/E60778_01/html/E60742/gkeza.html
    #endif  // at least version 5.14

    // Newer than Oracle Developer Studio 12.6 (CC version 5.15)
    #if BSLS_PLATFORM_CMP_VERSION >= 0x5150
      #define BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR                         1
        // CC 12.4 'constexpr' implementation almost satisfies our testing, but
        // the compiler crashes when for some rare-but-reasonable data
        // structures.  CC 12.5 has different corner cases, although we are
        // still trying to track down a narrowed test case.  Both 12.5 and
        // 12.6 have a regression compared to 12.4 though with the (implicit)
        // 'constexpr' constructors of aggregates that have dependent base
        // classes, such as most type traits.

      #define BSLS_COMPILERFEATURES_SUPPORT_DEFAULT_TEMPLATE_ARGS             1
        // CC 12.4, CC 12.5, and 12.6 all fail in a very specific way, which,
        // unfortunately, breaks for 'shared_ptr' in a way that is widely used.
        // Note that the version check assumes the next revision of the
        // compiler will have this fix, or the test driver will force us to
        // update again.
    #endif  // above version 5.15

    // Not yet CC version 5.16 (Studio 12.7?)
    #if BSLS_PLATFORM_CMP_VERSION < 0x5160
      #define BSLS_COMPILERFEATURES_INITIALIZER_LIST_LEAKS_ON_EXCEPTIONS      1
    #endif  // below version 5.16
  #endif  // C++11 or later

  // No C++14 features are available by default.  To use any C++14 features,
  // you must use the -std=c++14 option with the CC compiler.
  // '__cplusplus >= 201402L' when Oracle Solaris Studio 'CC -std=c++14' is
  // invoked.

  //CC -std=c++14
  #if  __cplusplus >= 201402L
    // Newer than Oracle Developer Studio 12.6 (CC version 5.15)
    #if BSLS_PLATFORM_CMP_VERSION > 0x5150
      #define BSLS_COMPILERFEATURES_SUPPORT_VARIABLE_TEMPLATES                1
    #endif  // above version 5.15
  #endif  // C++14 or later

  // No constexpr support
  // #define BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR_CPP14
  // #define BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR_CPP17

  // No '__include_next'
  // #define BSLS_COMPILERFEATURES_SUPPORT_INCLUDE_NEXT

  // No C++17 features
  // #define BSLS_COMPILERFEATURES_SUPPORT_HAS_INCLUDE
  // #define BSLS_COMPILERFEATURES_SUPPORT_HEXFLOAT_LITERALS
  // #define BSLS_COMPILERFEATURES_SUPPORT_NOEXCEPT_IN_FNC_TYPE

  // Oracle Solaris Studio does not yet follow WG14 N2322 Recommended practice
  // #define BSLS_COMPILERFEATURES_PP_LINE_IS_ON_FIRST
#endif  // Oracle Developer Studio

// ============================================================================
//                            DEPRECATED ALIASES
// ============================================================================

#ifdef BSLS_COMPILERFEATURES_SUPPORT_NOEXCEPT_IN_FNC_TYPE
  #define BSLS_COMPILERFEATURES_SUPPORT_NOEXCEPT_TYPES                        1
#endif

// ============================================================================
//                     STANDARD FEATURE-DETECTION MACROS
// ============================================================================

#if defined(__cpp_lib_is_constant_evaluated)
    #define BSLS_COMPILERFEATURES_SUPPORT_IS_CONSTANT_EVALUATED               1
#endif

// ============================================================================
//                DISABLE FEATURES REMOVED BY LATER STANDARDS
// ============================================================================

// Undefine macros defined for earlier dialects (including C++98) that are
// removed from later editions of the C++ Standard.

#if BSLS_COMPILERFEATURES_CPLUSPLUS >= 201703L
    #undef BSLS_COMPILERFEATURES_SUPPORT_THROW_SPECIFICATIONS
#endif

// ============================================================================
//                        ENFORCE LANGUAGE MODE
// ============================================================================

#if defined(BSLS_COMPILERFEATURES_FULL_CPP11)
# if BSLS_COMPILERFEATURES_CPLUSPLUS < 201103L
#    error C++11 is not enabled
# endif
#endif
#if defined(BSLS_COMPILERFEATURES_FULL_CPP14)
# if BSLS_COMPILERFEATURES_CPLUSPLUS < 201402L
#    error C++14 is not enabled
# endif
#endif
#if defined(BSLS_COMPILERFEATURES_FULL_CPP17)
# if BSLS_COMPILERFEATURES_CPLUSPLUS < 201703L
#    error C++17 is not enabled
# endif
#endif
#if defined(BSLS_COMPILERFEATURES_FULL_CPP20)
# if BSLS_COMPILERFEATURES_CPLUSPLUS < 202002L
#    error C++20 is not enabled
# endif
#endif
#if defined(BSLS_COMPILERFEATURES_FULL_CPP23)
# if BSLS_COMPILERFEATURES_CPLUSPLUS < 202302L
#    error C++23 is not enabled
# endif
#endif

// ============================================================================
//                        ENFORCE FEATURE INTERACTIONS
// ============================================================================

#if defined(BSLS_COMPILERFEATURES_SUPPORT_RVALUE_REFERENCES) &&              \
   !defined(BSLS_COMPILERFEATURES_SUPPORT_ALIAS_TEMPLATES)

    #undef BSLS_COMPILERFEATURES_SUPPORT_RVALUE_REFERENCES
        // BDE move-emulation for C++03 requires support for alias templates in
        // order to provide a transparent upgrade to the C++11 syntax that also
        // supports implicit-move from rvalues.
#endif

// ============================================================================
//                      SIMULATE VARIOUS C++11 FEATURES
// ============================================================================

#if !defined(BSLS_COMPILERFEATURES_SUPPORT_VARIADIC_TEMPLATES)

  #define BSLS_COMPILERFEATURES_SIMULATE_VARIADIC_TEMPLATES                   1

  #ifndef BSLS_COMPILERFEATURES_SIMULATE_CPP11_FEATURES
    #define BSLS_COMPILERFEATURES_SIMULATE_CPP11_FEATURES                     1
  #endif

  #if defined(__cplusplus) && BSLS_COMPILERFEATURES_SIMULATE_CPP11_FEATURES

    #define BSLS_COMPILERFEATURES_NILT BloombergLP::bsls::CompilerFeaturesNilT

    #define BSLS_COMPILERFEATURES_NILV BloombergLP::bsls::CompilerFeaturesNilV

    #define BSLS_COMPILERFEATURES_NILTR(n) BSLS_COMPILERFEATURES_NILT,

    #define BSLS_COMPILERFEATURES_FILLT(n)                                   \
        BSLS_MACROREPEAT(n, BSLS_COMPILERFEATURES_NILTR)                     \
                                                    BSLS_COMPILERFEATURES_NILT

    #define BSLS_COMPILERFEATURES_NILVR(n) BSLS_COMPILERFEATURES_NILV,

    #define BSLS_COMPILERFEATURES_FILLV(n)                                   \
        BSLS_MACROREPEAT(n,BSLS_COMPILERFEATURES_NILVR)                      \
                                                    BSLS_COMPILERFEATURES_NILV

namespace BloombergLP {
namespace bsls {

enum CompilerFeaturesNilT { COMPILERFEATURESNILV = 0x7fff6f76 };

}  // close package namespace
}  // close enterprise namespace

  #endif // C++ and BSLS_COMPILERFEATURES_SIMULATE_CPP11_FEATURES == 1
#endif // ! BSLS_COMPILERFEATURES_SUPPORT_VARIADIC_TEMPLATES

#ifndef BSLS_COMPILERFEATURES_SUPPORT_RVALUE_REFERENCES
  #define BSLS_COMPILERFEATURES_SIMULATE_FORWARD_WORKAROUND                   1

  #ifndef BSLS_COMPILERFEATURES_SIMULATE_CPP11_FEATURES
    #define BSLS_COMPILERFEATURES_SIMULATE_CPP11_FEATURES                     1
  #endif
#endif

#ifdef BSLS_COMPILERFEATURES_SIMULATE_FORWARD_WORKAROUND
  // Use a work-around for the absence of perfect-forwarding.

  #define BSLS_COMPILERFEATURES_FORWARD_REF(T) const T&
    // On compilers that support C++11 perfect forwarding, replace with 'T&&',
    // i.e., an argument that can be perfect-forwarded; otherwise, replace with
    // 'const T&', the classic way to accept arguments of unknown
    // rvalue/lvalue-ness.

  #define BSLS_COMPILERFEATURES_FORWARD(T,V)                                 \
                                        ::BloombergLP::bslmf::Util::forward(V)
    // On compilers that support C++11 perfect forwarding, replace with
    // 'bsl::forward<T>(V)', i.e., use perfect-forwarding; otherwise, replace
    // with '(V)', the classic way to forward arguments safely.

#else  // !defined simulate forwarding

  // Use real perfect-forwarding; no workaround needed.  Note that the explicit
  // 'BloombergLP' qualification is needed for 'bsls::Util' when it is used
  // from within namespace 'bsl', the BDE standard library implementation.

  #define BSLS_COMPILERFEATURES_FORWARD_REF(T) T&&

  #define BSLS_COMPILERFEATURES_FORWARD(T,V)                                 \
                                      ::BloombergLP::bsls::Util::forward<T>(V)

#endif  // forward-workaround for simulation

#endif  // header guard

// ----------------------------------------------------------------------------
// Copyright 2025 Bloomberg Finance L.P.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// ----------------------------- END-OF-FILE ----------------------------------
